Secreted PD-L1 variants mediate resistance to PD-L1 blockade therapy in non-small cell lung cancer

Soluble PD-L1 as a novel biomarker predicts poor outcomes and disease progression in de novo myelodysplastic syndromes

The role of the compromised immune microenvironment, including immune checkpoints, in myelodysplastic syndromes (MDS) has been identified as critical This study aimed to investigate the expression patterns of immune checkpoints, particularly soluble PD-1/PD-L1 (sPD-1/sPD-L1) as well as PD-1 on effector T cell subsets, and assess their prognostic value and potential regulatory roles in MDS. 161 MDS patients were enrolled, including 129 patients were primarily diagnosed with de novo MDS, together with 59 MDS patients who underwent hypomethylating agents (HMAs) therapy. Plasma sPD-L1 level was elevated in newly diagnosed MDS patients, which was also found to be associated with MDS disease progression that further increase in higher IPSS-R score group. Patients with increased sPD-L1 expression at diagnosis exhibited notably poorer overall survival, and multivariate Cox analysis indicated that elevated sPD-L1 was an independent risk factor. Furthermore, the levels of multiple cytokines and membrane-bound PD-1 on T cells were found to correlate with sPD-1/sPD-L1 levels in plasma. Importantly, we also found sPD-L1 levels significantly increased in MDS patients who showed progression of disease following HMAs therapy. In conclusion, we found elevated plasma sPD-L1 levels in MDS patients are associated with disease progression and poorer overall survival. This study showed that sPD-L1 is a potential biomarker for prognosis and a target for immunotherapy in MDS.

Tumor-derived exosomal ICAM1 promotes bone metastasis of triple-negative breast cancer by inducing CD8+ T cell exhaustion

Exosomes, which are nanosized extracellular vesicles, have emerged as crucial mediators of the crosstalk between tumor cells and the immune system. Intercellular adhesion molecule 1 (ICAM1) plays a crucial role in multiple immune functions as well as in the occurrence, development and metastasis of cancer. As a glycoprotein expressed on the cell membrane, ICAM1 is secreted extracellularly on exosomes and regulates the immunosuppressive microenvironment. However, the role of exosomal ICAM1 in the immune microenvironment of breast cancer bone metastases remains unclear. This study aimed to elucidated the role of exosomal ICAM1 in facilitating CD8+ T cell exhaustion and subsequent bone metastasis in triple-negative breast cancer (TNBC). We demonstrated that TNBC cells release ICAM1-enriched exosomes, and the binding of ICAM1 to its receptor is necessary for the suppressive effect of CD8 T cell proliferation and function. This pivotal engagement not only inhibits CD8+ T cell proliferation and activation but also initiates the development of an immunosuppressive microenvironment that is conducive to TNBC tumor growth and bone metastasis. Moreover, ICAM1 blockade significantly impairs the ability of tumor exosomes to bind to CD8+ T cells, thereby inhibiting their immunosuppressive effects. The present study elucidates the complex interaction between primary tumors and the immune system that is mediated by exosomes and provides a foundation for the development of novel cancer immunotherapies that target ICAM1 with the aim of mitigating TNBC bone metastasis.

PD-L1: From cancer immunotherapy to therapeutic implications in multiple disorders

The PD-L1/PD-1 signaling pathway is the gold standard for cancer immunotherapy. Therapeutic antibodies targeting PD-1, such as nivolumab (Opdivo) and pembrolizumab (Keytruda), and PD-L1, including atezolizumab (Tecentriq), durvalumab (Imfinzi), and avelumab (Bavencio) have received Food and Drug Administration approval and are currently being used to treat various cancers. Traditionally, PD-L1 is known as an immune checkpoint protein that binds to the PD-1 receptor on its surface to inhibit the activity of T cells, which are the primary effector cells in antitumor immunity. However, it also plays a role in cancer progression, which goes beyond traditional understanding. Here, we highlight the multifaceted mechanisms of action of PD-L1 in cancer cell proliferation, transcriptional regulation, and systemic immune suppression. Moreover, we consider the potential role of PD-L1 in the development and pathogenesis of diseases other than cancer, explore PD-L1-focused therapeutic approaches for these diseases, and assess their clinical relevance. Through this review, we hope to provide deeper insights into the PD-L1/PD-1 signaling pathway and present a broad perspective on potential therapeutic approaches for cancer and other diseases.

Mechanical force regulates ligand binding and function of PD-1

Despite the success of PD-1 blockade in cancer therapy, how PD-1 initiates signaling remains unclear. Soluble PD-L1 is found in patient sera and can bind PD-1 but fails to suppress T cell function. Here, we show that PD-1 function is reduced when mechanical support on ligand is removed. Mechanistically, cells exert forces to PD-1 and prolong bond lifetime at forces <7 pN (catch bond) while accelerate dissociation at forces >8pN (slip bond). Molecular dynamics of PD-1-PD-L2 complex suggests force may cause relative rotation and translation between the two molecules yielding distinct atomic contacts not observed in the crystal structure. Compared to wild-type, PD-1 mutants targeting the force-induced distinct interactions maintain the same binding affinity but suppressed/eliminated catch bond, lowered rupture force, and reduced inhibitory function. Our results uncover a mechanism for cells to probe the mechanical support of PD-1-PD-Ligand bonds using endogenous forces to regulate PD-1 signaling.

Soluble Tim-3 serves as a tumor prognostic marker and therapeutic target for CD8+ T cell exhaustion and anti-PD-1 resistance

Resistance to PD-1 blockade in onco-immunotherapy greatly limits its clinical application. T cell immunoglobulin and mucin domain containing-3 (Tim-3), a promising immune checkpoint target, is cleaved by ADAM10/17 to produce its soluble form (sTim-3) in humans, potentially becoming involved in anti-PD-1 resistance. Herein, serum sTim-3 upregulation was observed in non-small cell lung cancer (NSCLC) and various digestive tumors. Notably, serum sTim-3 is further upregulated in non-responding patients undergoing anti-PD-1 therapy for NSCLC and anti-PD-1-resistant cholangiocarcinoma patients. Furthermore, sTim-3 overexpression facilitates tumor progression and confers anti-PD-1 resistance in multiple tumor mouse models. Mechanistically, sTim-3 induces terminal T cell exhaustion and attenuates CD8+ T cell response to PD-1 blockade through carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM-1). Moreover, the ADAM10 inhibitor GI254023X, which blocks sTim-3 production, reduces tumor progression in Tim-3 humanized mice and reverses anti-PD-1 resistance in human tumor-infiltrating lymphocytes (TILs). Overall, human sTim-3 holds great predictive and therapeutic potential in onco-immunotherapy.

Platelet PD-L1 inhibits storage-induced apoptosis by sustaining activation of the AKT signalling pathway

Platelet apoptosis is irreversible under current storage conditions in blood banks. Studies have shown that programmed cell death ligand 1 (PD-L1) in tumour cells is required for neoplastic progression, tumour recurrence and metastasis by regulating apoptosis. However, whether PD-L1 is involved in storage-induced apoptosis in platelets remains poorly understood. In this study, we explored whether PD-L1 on platelets participated in the regulation of storage-induced apoptosis under blood bank conditions, as well as the underlying mechanism. Several apoptotic events in platelets from humans and PD-L1-knockout mice during storage under blood bank conditions were measured. The mechanism by which storage-induced apoptosis was regulated by platelet-intrinsic PD-L1 signalling was further investigated. Our results showed that PD-L1 in platelets progressively decreased. There was a strong negative correlation between platelet PD-L1 expression and the phosphatidylserine (PS) externalization rate and cleaved caspase-3 level and a positive correlation with anti-apoptosis protein Bcl-xl. Ex vivo, PD-L1-/- platelets stored at 22 °C showed rapid apoptosis via an intrinsic mitochondria-dependent pathway over time. Likewise, inhibiting PD-L1 signalling with BMS-1166 accelerated apoptosis by intrinsic mitochondria-dependent pathway. Coimmunoprecipitation analysis revealed that PD-L1 could bind AKT in platelets, and the binding capacity of both showed a progressive decrease with time. Finally, the decrease in PD-L1 expression levels during storage could be attributed to a complex process of progressive secretion. Therefore, platelet PD-L1 inhibits storage-induced apoptosis by sustaining activation of the AKT signalling pathway, which is expected to become a target for alleviating platelet storage lesions (PSLs) under current blood bank conditions.

Pt-Te-Nanorod-Based Photothermal Chemokine Immunotherapy for All Stages of Cancer via Adaptive and Innate Immunity

The chemokine (C-X-C) motif ligand 9 (CXCL9) is one of the lymphocyte-traffic-involved chemokines. Despite the immunotherapeutic potential of CXCL9 for recruiting effector T cells (cluster of differentiation 4+ (CD4+) and CD8+ T cells) and natural killer cells (NK cells) around the tumors, practical applications of CXCL9 have been limited because of its immune toxicity and lack of stability in vivo. To overcome these limitations, we designed and synthesized Pt-Te nanorods (PtTeNRs), which exhibited excellent photothermal conversion efficiency with stable CXCL9 payload characteristics under the physiological conditions of in vivo environments. We developed a CXCL9-based immunotherapy strategy by utilizing the unique physicochemical properties of developed PtTeNRs. The investigation revealed that the PtTeNR-loaded CXCL9 was effectively accumulated in the tumor, subsequently released in a sustained manner, and successfully recruited effector T cells for immunotherapy of the designated tumor tissue. In addition, a synergistic effect was observed between the photothermal (PT) therapy and antiprogrammed cell death protein 1 (aPD-1) antibody. In this study, we demonstrated that PtTeNR-based CXCL9, PT, and aPD-1 antibody trimodal therapy delivers an outstanding tumor suppression effect in all stages of cancer, including phases 1-4 and tumor recurrence.

Biomarker development for PD-(L)1 axis inhibition: a consensus view from the SITC Biomarkers Committee

Therapies targeting the programmed cell death protein-1/programmed death-ligand 1 (PD-L1) (abbreviated as PD-(L)1) axis are a significant advancement in the treatment of many tumor types. However, many patients receiving these agents fail to respond or have an initial response followed by cancer progression. For these patients, while subsequent immunotherapies that either target a different axis of immune biology or non-immune combination therapies are reasonable treatment options, the lack of predictive biomarkers to follow-on agents is impeding progress in the field. This review summarizes the current knowledge of mechanisms driving resistance to PD-(L)1 therapies, the state of biomarker development along this axis, and inherent challenges in future biomarker development for these immunotherapies. Innovation in the development and application of novel biomarkers and patient selection strategies for PD-(L)1 agents is required to accelerate the delivery of effective treatments to the patients most likely to respond.

PD-L1 at the crossroad between RNA metabolism and immunosuppression

Programmed death ligand-1 (PD-L1) is a key component of tumor immunosuppression. The uneven therapeutic results of PD-L1 therapy have stimulated intensive studies to better understand the mechanisms underlying altered PD-L1 expression in cancer cells, and to determine whether, beyond its immune function, PD-L1 might have intracellular functions promoting tumor progression and resistance to treatments. In this Opinion, we focus on paradigmatic examples highlighting the central role of PD-L1 in post-transcriptional regulation, with PD-L1 being both a target and an effector of molecular mechanisms featured prominently in RNA research, such as RNA methylation, phase separation and RNA G-quadruplex structures, in order to highlight vulnerabilities on which future anti-PD-L1 therapies could be built.

A Comparison of Cellular Immune Response and Immunological Biomarkers in Laparoscopic Surgery for Colorectal Cancer and Benign Disorders

BACKGROUND

Surgical trauma causes immune impairment, but it is largely unknown whether surgery for cancer and benign diseases instigate comparable levels of immune inhibition. Here, we compared the impact of laparoscopic surgery on immunological biomarkers in patients with colorectal cancer (CRC) and ventral hernia (VH).

METHODS

Natural Killer cell activity (NKA), leukocyte subsets, and soluble programmed death ligand 1 (sPD-L1) were measured in blood samples collected from CRC (n = 29) and VH (n = 9) patients preoperatively (PREOP) and on postoperative day (POD) 1, 3-6, 2 weeks and 3 months. NKA was evaluated by the NK Vue assay that uses the level of IFNγ as a surrogate marker of NKA. Normal NKA was defined as IFNγ > 250 pg/mL and low NKA was defined as IFNγ < 250 pg/mL.

RESULTS

The CRC cohort was classified into either PREOPLOW having preoperative low NKA or PREOPHIGH having preoperative normal NKA. The median NKA of the PREOPLOW subset was only in the normal range in the POD3 months sample, whereas median NKA of the PREOPHIGH subset and the VH cohort were only low in the POD1 sample. While PREOPLOW differed from VH in the PREOP-, POD1-, and POD3-6 samples (P =.0006, P = .0181, and P = .0021), NKA in PREOPHIGH and VH differed in the POD1 samples (P = .0226). There were no apparent differences in the distribution of leukocyte subsets in the perioperative period between the cohorts.

CONCLUSION

CRC patients with preoperative normal NKA and VH patients showed the same pattern of recovery in NKA, while the CRC subset with preoperative low NKA seemed to experience prolonged NK cell impairment. As low NKA is associated with recurrence, preoperative level of NKA may identify patients who will benefit from immune-enhancing therapy in the perioperative period.

Small extracellular vesicles: Multi-functional aspects in non-small cell lung carcinoma

Extracellular vesicles (EVs) impact normal and pathological cellular signaling through bidirectional trafficking. Exosomes, a subset of EVs possess biomolecules including proteins, lipids, DNA fragments and various RNA species reflecting a speculum of their parent cells. The involvement of exosomes in bidirectional communication and their biological constituents substantiate its role in regulating both physiology and pathology, including multiple cancers. Non-small cell lung cancer (NSCLC) is the most common lung cancers (85%) with high incidence, mortality and reduced overall survival. Lack of efficient early diagnostic and therapeutic tools hurdles the management of NSCLC. Interestingly, the exosomes from body fluids similarity with parent cells or tissue offers a potential future multicomponent tool for the early diagnosis of NSCLC. The structural twinning of exosomes with a cell/tissue and the competitive tumor derived exosomes in tumor microenvironment (TME) promotes the unpinning horizons of exosomes as a drug delivery, vaccine, and therapeutic agent. Exosomes in clinical point of view assist to trace: acquired resistance caused by various therapeutic agents, early diagnosis, progression, and surveillance. In an integrated approach, EV biomarkers offer potential cutting-edge techniques for the detection and diagnosis of cancer, though the purification, characterization, and biomarker identification processes for the translational research regarding EVs need further optimization.

Plasma sPD-L1 and VEGF levels are associated with the prognosis of NSCLC patients treated with combination immunotherapy

The clinical significance of plasma soluble programmed cell death ligand 1 (sPD-L1) and vascular endothelial growth factor (VEGF) for non-small cell lung cancer (NSCLC) treated with the combination of anti-angiogenic therapy and anti-PD-L1 antibody (Ab) remain unknown. This study aimed to explore the association between plasma sPD-L1 and VEGF levels and the prognosis of NSCLC patients treated with the combination of Envafolimab and Endostar. Peripheral blood samples were collected from 24 NSCLC patients at baseline and after 6 weeks of treatment and were detected for sPD-L1 and VEGF levels. Both baseline and posttreatment sPD-L1 were significantly higher in progressive disease (PD) group than in controlled disease (CD) group (median: 77.5 pg/ml vs. 64.6 pg/ml, P  = 0.036, median: 8451 pg/ml vs. 5563 pg/ml, P  = 0.012). In multivariate analysis, lower baseline sPD-L1 levels were significantly associated with longer progression-free survival (PFS) (HR = 6.834, 95% CI: 1.350-34.592, P  = 0.020). There were significantly higher posttreatment VEGF levels in PD group compared with CD group (median: 323.7 pg/ml vs. 178.5 pg/ml, P  = 0.009). Higher posttreatment VEGF levels were significantly associated with shorter PFS in multivariate analysis (HR = 5.911, 95% CI: 1.391-25.122, P  = 0.016). Plasma sPD-L1 and VEGF levels are associated with the clinical response and prognosis of NSCLC patients treated with the combination of PD-L1 inhibitors and anti-angiogenetic therapy.

Soluble immune checkpoints: implications for cancer prognosis and response to immune checkpoint therapy and conventional therapies

Longitudinal sampling of tumor tissue from patients with solid cancers, aside from melanoma and a few other cases, is often unfeasible, and thus may not capture the plasticity of interactions between the tumor and immune system under selective pressure of a given therapy. Peripheral blood analyses provide salient information about the human peripheral immunome while offering technical and practical advantages over traditional tumor biopsies, and should be utilized where possible alongside interrogation of the tumor. Some common blood-based biomarkers used to study the immune response include immune cell subsets, circulating tumor DNA, and protein analytes such as cytokines. With the recent explosion of immune checkpoint inhibitors (ICI) as a modality of treatment in multiple cancer types, soluble immune checkpoints have become a relevant area of investigation for peripheral immune-based biomarkers. However, the exact functions of soluble immune checkpoints and their roles in cancer for the most part remain unclear. This review discusses current literature on the production, function, and expression of nine soluble immune checkpoints - sPD-L1, sPD-1, sCTLA4, sCD80, sTIM3, sLAG3, sB7-H3, sBTLA, and sHVEM - in patients with solid tumors, and explores their role as biomarkers of response to ICI as well as to conventional therapies (chemotherapy, radiotherapy, targeted therapy, and surgery) in cancer patients.

Therapeutic Implications of Targeting YY1 in Glioblastoma

The transcription factor Yin Yang 1 (YY1) plays a pivotal role in the pathogenesis of glioblastoma multiforme (GBM), an aggressive form of brain tumor. This review systematically explores the diverse roles of YY1 overexpression and activities in GBM, including its impact on the tumor microenvironment (TME) and immune evasion mechanisms. Due to the poor response of GBM to current therapies, various findings of YY1-associated pathways in the literature provide valuable insights into novel potential targeted therapeutic strategies. Moreover, YY1 acts as a significant regulator of immune checkpoint molecules and, thus, is a candidate therapeutic target in combination with immune checkpoint inhibitors. Different therapeutic implications targeting YY1 in GBM and its inherent associated challenges encompass the use of nanoparticles, YY1 inhibitors, targeted gene therapy, and exosome-based delivery systems. Despite the inherent complexities of such methods, the successful targeting of YY1 emerges as a promising avenue for reshaping GBM treatment strategies, presenting opportunities for innovative therapeutic approaches and enhanced patient outcomes.

TRAF6 enhances PD-L1 expression through YAP1-TFCP2 signaling in melanoma

Immunotherapy represented by programmed cell death protein 1 (PD-1)/programmed death ligand 1 (PD-L1) monoclonal antibodies has led tumor treatment into a new era. However, the low overall response rate and high incidence of drug resistance largely damage the clinical benefits of existing immune checkpoint therapies. Recent studies correlate the response to PD-1/PD-L1 blockade with PD-L1 expression levels in tumor cells. Hence, identifying molecular targets and pathways controlling PD-L1 protein expression and stability in tumor cells is a major priority. In this study, we performed a Stress and Proteostasis CRISPR interference screening to identify PD-L1 positive modulators. Here, we identified TRAF6 as a critical regulator of PD-L1 in melanoma cells. As a non-conventional E3 ubiquitin ligase, TRAF6 is inclined to catalyze the synthesis and linkage of lysine-63 (K63) ubiquitin which is related to the stabilization of substrate proteins. Our results showed that suppression of TRAF6 expression down-regulates PD-L1 expression on the membrane surface of melanoma cells. We then used in vitro and in vivo assays to investigate the biological function and mechanism of TRAF6 and its downstream YAP1/TFCP2 signaling in melanoma. TRAF6 stabilizes YAP1 by K63 poly-ubiquitination modification, subsequently promoting the formation of YAP1/TFCP2 transcriptional complex and PD-L1 transcription. Inhibition of TRAF6 by Bortezomib enhanced cytolytic activity of CD8+ T cells by reduction of endogenous PD-L1. Notably, Bortezomib enhances anti-tumor immunity to an extent comparable to anti-PD-1 therapies with no obvious toxicity. Our findings reveal the potential of inhibiting TRAF6 to stimulate internal anti-tumor immunological effect for TRAF6-PD-L1 overexpressing cancers.

Regulatory mechanisms of PD-1/PD-L1 in cancers

Immune evasion contributes to cancer growth and progression. Cancer cells have the ability to activate different immune checkpoint pathways that harbor immunosuppressive functions. The programmed death protein 1 (PD-1) and programmed cell death ligands (PD-Ls) are considered to be the major immune checkpoint molecules. The interaction of PD-1 and PD-L1 negatively regulates adaptive immune response mainly by inhibiting the activity of effector T cells while enhancing the function of immunosuppressive regulatory T cells (Tregs), largely contributing to the maintenance of immune homeostasis that prevents dysregulated immunity and harmful immune responses. However, cancer cells exploit the PD-1/PD-L1 axis to cause immune escape in cancer development and progression. Blockade of PD-1/PD-L1 by neutralizing antibodies restores T cells activity and enhances anti-tumor immunity, achieving remarkable success in cancer therapy. Therefore, the regulatory mechanisms of PD-1/PD-L1 in cancers have attracted an increasing attention. This article aims to provide a comprehensive review of the roles of the PD-1/PD-L1 signaling in human autoimmune diseases and cancers. We summarize all aspects of regulatory mechanisms underlying the expression and activity of PD-1 and PD-L1 in cancers, including genetic, epigenetic, post-transcriptional and post-translational regulatory mechanisms. In addition, we further summarize the progress in clinical research on the antitumor effects of targeting PD-1/PD-L1 antibodies alone and in combination with other therapeutic approaches, providing new strategies for finding new tumor markers and developing combined therapeutic approaches.

Lysosomal degradation of PD-L1 is associated with immune-related adverse events during anti-PD-L1 immunotherapy in NSCLC patients

Background: Immune checkpoint inhibitors (ICIs) can induce immune-related adverse events (irAEs). Liquid biomarkers to predict irAE occurrence are urgently needed. We previously developed an ELISA system to specifically detect soluble PD-L1 (sPD-L1) with PD-1-binding capacity (bsPD-L1). Here, we investigated the relationship between sPD-L1 and bsPD-L1 in gastric cancer (GC) and non-small cell lung cancer (NSCLC) treated with PD-1/PD-L1 blockade and their association with irAEs. Methods: We examined sPD-L1, bsPD-L1, matrix metalloproteinases (MMPs), and proinflammatory cytokine levels by ELISA in plasma samples from 117 GC patients prior to surgery and 72 NSCLC patients prior to and at 2 months after ICI treatment (anti-PD-1, n = 48; anti-PD-L1, n = 24). In mice treated with anti-PD-1/PD-L1 antibodies (Abs), sPD-L1 levels and localization of Abs were examined by ELISA and immunohistochemistry, respectively. Results:sPD-L1 was detected with higher frequency in GC patients than in NSCLC patients, whereas bsPD-L1 was detected with similar frequencies in GC and NSCLC patients. sPD-L1 levels were correlated with IL-1α, IL-1β, TNF-α, and IL-6 levels, while bsPD-L1 levels were correlated with MMP13, MMP3, and IFN-γ levels. In NSCLC patients, anti-PD-L1, but not anti-PD-1, treatment increased sPD-L1, which was associated with irAE development, but not with clinical outcomes. In mice, trafficking of anti-PD-L1 Abs to lysosomes in F4/80+ macrophages resulted in sPD-L1 production, which was suppressed by treatment with lysosomal degradation inhibitor chloroquine and macrophage depletion. Conclusion: Anti-PD-L1-mediated lysosomal degradation induces sPD-L1 production, which can serve as an indicator to predict irAE development during anti-PD-L1 treatment.

Combination of plasma MMPs and PD-1-binding soluble PD-L1 predicts recurrence in gastric cancer and the efficacy of immune checkpoint inhibitors in non-small cell lung cancer

Background

The tumor microenvironment (TME) impacts the therapeutic efficacy of immune checkpoint inhibitors (ICIs). No liquid biomarkers are available to evaluate TME heterogeneity. Here, we investigated the clinical significance of PD-1-binding soluble PD-L1 (bsPD-L1) in gastric cancer (GC) patients and non-small cell lung cancer (NSCLC) patients treated with PD-1/PD-L1 blockade.

Methods

We examined bsPD-L1, matrix metalloproteinases (MMPs), and IFN-γ levels in plasma samples from GC patients (n = 117) prior to surgery and NSCLC patients (n = 72) prior to and 2 months after ICI treatment. We also examined extracellular matrix (ECM) integrity, PD-L1 expression, and T cell infiltration in tumor tissues from 25 GC patients by Elastica Masson-Goldner staining and immunohistochemical staining for PD-L1 and CD3, respectively.

Results

bsPD-L1 was detected in 17/117 GC patients and 16/72 NSCLC patients. bsPD-L1 showed strong or moderate correlations with plasma MMP13 or MMP3 levels, respectively, in both GC and NSCLC patients. bsPD-L1 expression in GC was associated with IFN-γ levels and intra-tumoral T cell infiltration, whereas MMP13 levels were associated with loss of ECM integrity, allowing tumor cells to access blood vessels. Plasma MMP3 and MMP13 levels were altered during ICI treatment. Combined bsPD-L1 and MMP status had higher predictive accuracy to identify two patient groups with favorable and poor prognosis than tumor PD-L1 expression: bsPD-L1+MMP13high in GC and bsPD-L1+(MMP3 and MMP13)increased in NSCLC were associated with poor prognosis, whereas bsPD-L1+MMP13low in GC and bsPD-L1+(MMP3 or MMP13)decreased in NSCLC were associated with favorable prognosis.

Conclusion

Plasma bsPD-L1 and MMP13 levels indicate T cell response and loss of ECM integrity, respectively, in the TME. The combination of bsPD-L1 and MMPs may represent a non-invasive tool to predict recurrence in GC and the efficacy of ICIs in NSCLC.

Clinical significance of inter-assay discrepancy in PD-L1 evaluation for the efficacy of pembrolizumab in advanced NSCLC with high PD-L1 expression

INTRODUCTION

Programmed cell death ligand-1 (PD-L1) expression is a predictive biomarker for the efficacy of anti-programmed cell death receptor-1/PD-L1 antibodies in advanced non-small cell lung cancer (NSCLC). Although several assays have been approved for evaluating PD-L1 expression status, inter-assay discordance has been observed between some assays. The clinical significance of these discrepancies is still unclear.

METHODS

We retrospectively reviewed treatment-naïve NSCLC patients whose PD-L1 expression was evaluated using both 22C3 and SP142 assays. Among those, efficacy analysis was performed for patients with PD-L1 tumor proportion score (TPS) ≥ 50 % (22C3), who had received first-line pembrolizumab monotherapy. Additionally, transcriptome analysis was conducted in the available tumors with TPS ≥ 50 % to investigate the distinct immune profiles that accompany inter-assay discordance.

RESULTS

In total, 611 patients were eligible. Among 198 patients with TPS ≥ 50 %, 91 (46 %) had tumor cell score ≤ 1 (SP142, i.e., inter-assay discrepancy). In the 52 patients who received first-line pembrolizumab monotherapy, treatment efficacy was significantly lower in patients with the discrepancy than that in those without (objective response rate: 18 % vs. 83 %, p < 0.001; median progression-free survival [months]: 3.2 vs. 8.3, p < 0.001). Transcriptome analysis revealed significantly more CD274 splice variants with aberrant 3'-terminal sequences in tumors with the inter-assay discrepancy than in those without.

CONCLUSION

The inter-assay discrepancy in the PD-L1 status of tumor cells between the 22C3 and SP142 assays, reflecting an imbalance in the CD274 splice variants, could be a biomarker for primary resistance against pembrolizumab monotherapy in high PD-L1-expressing NSCLCs.

Emerging therapeutic frontiers in cancer: insights into posttranslational modifications of PD-1/PD-L1 and regulatory pathways

The interaction between programmed cell death ligand 1 (PD-L1), which is expressed on the surface of tumor cells, and programmed cell death 1 (PD-1), which is expressed on T cells, impedes the effective activation of tumor antigen-specific T cells, resulting in the evasion of tumor cells from immune-mediated killing. Blocking the PD-1/PD-L1 signaling pathway has been shown to be effective in preventing tumor immune evasion. PD-1/PD-L1 blocking antibodies have garnered significant attention in recent years within the field of tumor treatments, given the aforementioned mechanism. Furthermore, clinical research has substantiated the efficacy and safety of this immunotherapy across various tumors, offering renewed optimism for patients. However, challenges persist in anti-PD-1/PD-L1 therapies, marked by limited indications and the emergence of drug resistance. Consequently, identifying additional regulatory pathways and molecules associated with PD-1/PD-L1 and implementing judicious combined treatments are imperative for addressing the intricacies of tumor immune mechanisms. This review briefly outlines the structure of the PD-1/PD-L1 molecule, emphasizing the posttranslational modification regulatory mechanisms and related targets. Additionally, a comprehensive overview on the clinical research landscape concerning PD-1/PD-L1 post-translational modifications combined with PD-1/PD-L1 blocking antibodies to enhance outcomes for a broader spectrum of patients is presented based on foundational research.

Soluble programmed death ligand 1 as prognostic biomarker in non-small cell lung cancer patients receiving nivolumab, pembrolizumab or atezolizumab therapy

Many studies have focused on the prognostic role of soluble programmed death ligand 1 (sPD-L1) in non-small cell lung cancer (NSCLC), but outcomes are ambiguous and further investigations are needed. We addressed the matter by studying sPD-L1 in baseline samples and in longitudinal samples taken prior to three subsequent cycles of anti-PD-1/anti-PD-L1 treatments. Eighty patients with NSCLC were enrolled. Median sPD-L1 level at baseline was 52 pg/mL [95% confidence interval (CI) 49-57]. In patients treated with pembrolizumab and nivolumab, the concentration of sPD-L1 remained rather stable throughout treatment. In contrast, sPD-L1 rose by 50-fold following the first cycle of atezolizumab therapy. We found the baseline level of sPD-L1 to be related to overall survival (OS) after two years of follow-up in simple Cox analysis (p = 0.006) and multiple Cox Regression, hazard ratio 1.02 (95% CI 1.00-1.03) (p = 0.033). There was no association between sPD-L1 and tissue PD-L1 expression, overall response rate, or progression free survival. In conclusion, sPD-L1 measured in baseline serum samples may be associated with OS in NSCLC patients receiving anti-PD1/anti-PD-L1 treatment. Importantly, the results signify that further research is warranted to explore the clinical utility of sPD-L1 in patients treated with anti-PD-L1.

Inhibition of ATM promotes PD-L1 expression by activating JNK/c-Jun/TNF-α signaling axis in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is a heterogeneous subtype of breast cancer. Anti-PD-1/PD-L1 treatment for advanced TNBC is still limited to PD-L1-positive patients. Ataxia telangiectasia mutated (ATM) is a switch molecule for homologous recombination and repair. In this study, we found a significant negative correlation between ATM and PD-L1 in 4 TNBC clinical specimens by single-cell RNA sequencing (scRNA-seq), which was confirmed by immunochemical staining in 86 TNBC specimens. We then established ATM knockdown TNBC stable cell lines to perform in vitro studies and animal experiments, proving the negative regulation of PD-L1 by ATM via suppression of tumor necrosis factor-alpha (TNF-α), which was confirmed by cytokine array analysis of TNBC cell line and analysis of clinical specimens. We further found that ATM inhibits TNF-α via inactivating JNK/c-Jun by scRNA-seq, Western blot and luciferase reporter assays. Finally, we identified a negative correlation between changes in phospho-ATMS1981 and PD-L1 levels in TNBC post- and pre-neoadjuvant therapy. This study reveals a novel mechanism by which ATM negatively regulates PD-L1 by downregulating JNK/c-Jun/TNF-α in TNBC, shedding light on the wide application of immune checkpoint blockade therapy for treating multi-line-resistant TNBC.

Restoration of miR-299-3p promotes macrophage phagocytosis and suppresses malignant phenotypes in breast cancer carcinogenesis via dual-targeting CD47 and ABCE1

Immunoevasion has been a severe obstacle for the clinical treatment of breast cancer (BC). CD47, known as an anti-phagocytic molecule, plays a key role in governing the evasion of tumor cells from immune surveillance by interacting with signal-regulated protein α (SIRPα) on macrophages. Here, we report for the first time that miR-299-3p is a direct regulator of CD47 with tumor suppressive effects both in vitro and in vivo. miRNA expression profiles and overall survival of BC cohorts from the Cancer Genome Atlas, METABRIC, or GSE19783 datasets showed that miR-299-3p is downregulated in BC tissues and that BC patients with low levels of miR-299-3p have poorer prognoses. Using dual-luciferase reporter, qRT-PCR, Western blot, and phagocytosis assays, we proved that restoration of miR-299-3p can suppress CD47 expression by directly targeting the predicted seed sequence "CCCACAU" in its 3'-UTR, leading to phagocytosis of BC cells by macrophages, whereas miR-299-3p inhibition or deletion reversed this effect. Additionally, Gene Ontology (GO) analysis and a variety of confirmatory experiments revealed that miR-299-3p was inversely correlated with cell proliferation, migration, and the cell cycle process. Mechanistically, miR-299-3p can also directly target ABCE1, an essential ribosome recycling factor, alleviating these malignant phenotypes of BC cells. In vivo BC xenografts based on nonobese diabetic/severe combined immunodeficient (NOD/SCID) mice further proved that restoration of miR-299-3p resulted in a significant suppression of tumorigenesis and a promotion of macrophage activation and infiltration. Overall, our study suggested that miR-299-3p is a potent inhibitor of CD47 and ABCE1 to exhibit bifunctional BC-suppressing effects through immune activation conjugated with malignant behavior inhibition in breast carcinogenesis and thus can potentially serve as a novel therapeutic target for BC.

Identification of the exosomal PD-L1 inhibitor to promote the PD-1 targeting therapy of gastric cancer

Programmed death 1/programmed death-ligand 1 (PD-1/PD-L1) targeting therapy is widely applied in clinics for gastric cancer treatment. Nevertheless, the clinical response is not well acceptable due to the exosomal PD-L1. Hence, abrogation of the exosomal PD-L1 may be a strategy to sensitize the gastric cancer cell to PD-1 targeting therapy. With the aid of CD63 targeting antibody and PD-L1 targeting aptamer, HTRF based assay was established to quantify the exosomal PD-L1, and applied to our in-house compound library, resulting in the identification of moclobemide. Further optimization of moclobemide lead to EP16, which can inhibit the generation of exosomal PD-L1 with IC50 = 0.108 μM. By applying EP16 to gastric cancer cell line coupled with T-cell activity related experiment, it was validated to activate T-cell and can promote the response of PD-1 targeting therapy for gastric cancer treatment in vitro and in vivo. Collectively, our findings give a promising tool to promote the sensitivity of anti-PD-1 for gastric cancer treatment, and EP16 can serve as a leading compound for exosomal PD-L1 abrogation.

The B7:CD28 family and friends: Unraveling coinhibitory interactions

Immune responses must be tightly regulated to ensure both optimal protective immunity and tolerance. Costimulatory pathways within the B7:CD28 family provide essential signals for optimal T cell activation and clonal expansion. They provide crucial inhibitory signals that maintain immune homeostasis, control resolution of inflammation, regulate host defense, and promote tolerance to prevent autoimmunity. Tumors and chronic pathogens can exploit these pathways to evade eradication by the immune system. Advances in understanding B7:CD28 pathways have ushered in a new era of immunotherapy with effective drugs to treat cancer, autoimmune diseases, infectious diseases, and transplant rejection. Here, we discuss current understanding of the mechanisms underlying the coinhibitory functions of CTLA-4, PD-1, PD-L1:B7-1 and PD-L2:RGMb interactions and less studied B7 family members, including HHLA2, VISTA, BTNL2, and BTN3A1, as well as their overlapping and unique roles in regulating immune responses, and the therapeutic potential of these insights.

Mechanisms of Resistance and Therapeutic Perspectives in Immunotherapy for Advanced Head and Neck Cancers

Immunotherapy is emerging as an effective treatment for advanced head and neck cancers and interest in this treatment modality has led to rapid expansion of this research. Pembrolizumab and nivolumab, monoclonal antibodies directed against the programmed cell death-1 (PD-1) receptor, are US Food and Drug Administration (FDA)- and European Medical Agency (EMA)-approved immunotherapies for head and neck squamous cell carcinoma (HNSCC). Resistance to immunotherapy is common, with about 60% of patients with recurrent or metastatic HNSCC not responding to immunotherapy and only 20-30% of patients without disease progression in the long term. Overcoming resistance to immunotherapy is therefore essential for augmenting the effectiveness of immunotherapy in HNSCC. This review details the innate and adaptive mechanisms by which head and neck cancers can become resistant to immunotherapeutic agents, biomarkers that can be used for immunotherapy patient selection, as well as other factors of the tumor microenvironment correlated with therapeutic response and prognosis. Numerous combinations and novel immunotherapies are currently being trialed, based on better understood immune evasion mechanisms. These potential treatments hold the promise of overcoming resistance to immunotherapy in head and neck cancers.

Extracellular vesicles as tools and targets in therapy for diseases

Extracellular vesicles (EVs) are nano-sized, membranous structures secreted into the extracellular space. They exhibit diverse sizes, contents, and surface markers and are ubiquitously released from cells under normal and pathological conditions. Human serum is a rich source of these EVs, though their isolation from serum proteins and non-EV lipid particles poses challenges. These vesicles transport various cellular components such as proteins, mRNAs, miRNAs, DNA, and lipids across distances, influencing numerous physiological and pathological events, including those within the tumor microenvironment (TME). Their pivotal roles in cellular communication make EVs promising candidates for therapeutic agents, drug delivery systems, and disease biomarkers. Especially in cancer diagnostics, EV detection can pave the way for early identification and offers potential as diagnostic biomarkers. Moreover, various EV subtypes are emerging as targeted drug delivery tools, highlighting their potential clinical significance. The need for non-invasive biomarkers to monitor biological processes for diagnostic and therapeutic purposes remains unfulfilled. Tapping into the unique composition of EVs could unlock advanced diagnostic and therapeutic avenues in the future. In this review, we discuss in detail the roles of EVs across various conditions, including cancers (encompassing head and neck, lung, gastric, breast, and hepatocellular carcinoma), neurodegenerative disorders, diabetes, viral infections, autoimmune and renal diseases, emphasizing the potential advancements in molecular diagnostics and drug delivery.

The emerging roles of PD-L1 subcellular localization in tumor immune evasion

Targeting immune checkpoint PD-1 or its ligand PD-L1 blockade has achieved a great therapeutic effect in a variety of cancer types. However, the overall response rate and duration are still limited for intrinsic and acquired resistance. There is an urgent need to understand the underlying mechanism. Studies showed that PD-L1 regulation is related to the response to PD-1 monoclonal antibodies (PD-1 mAB). Interestingly, emerging studies found that the different distribution of PD-L1 has distinct functions in tumor through the specific signaling pathways. Thus, controlling the distribution of PD-L1 provides an attractive therapeutic strategy for enhancing PD-1 mAB efficiency and rewiring the resistance. Here, we review the recent studies about the role and regulation of PD-L1 distribution from synthesis to surface delivery, internalization, recycling, or lysosome degradation and translocated into the nucleus or secreted into the extracellular space. We place this knowledge in the context of observations in the clinic and discuss the potential therapeutic strategies to enhance the efficacy of anti-PD-1/PD-L1 therapy.

Roles of exosomes in immunotherapy for solid cancers

Although immunotherapy has made breakthrough progress, its efficacy in solid tumours remains unsatisfactory. Exosomes are the main type of extracellular vesicles that can deliver various intracellular molecules to adjacent or distant cells and organs, mediating various biological functions. Studies have found that exosomes can both activate the immune system and inhibit the immune system. The antigen and major histocompatibility complex (MHC) carried in exosomes make it possible to develop them as anticancer vaccines. Exosomes derived from blood, urine, saliva and cerebrospinal fluid can be used as ideal biomarkers in cancer diagnosis and prognosis. In recent years, exosome-based therapy has made great progress in the fields of drug transportation and immunotherapy. Here, we review the composition and sources of exosomes in the solid cancer immune microenvironment and further elaborate on the potential mechanisms and pathways by which exosomes influence immunotherapy for solid cancers. Moreover, we summarize the potential clinical application prospects of engineered exosomes and exosome vaccines in immunotherapy for solid cancers. Eventually, these findings may open up avenues for determining the potential of exosomes for diagnosis, treatment, and prognosis in solid cancer immunotherapy.

Adjuvant immunotherapy in patients with renal cell carcinoma and urothelial carcinoma: A systematic review and network meta-analysis

Adjuvant immune checkpoint inhibitor therapies have radically altered the treatment landscape for renal cell carcinoma and urothelial carcinoma. However, studies have reported negative data regarding adjuvant immune checkpoint inhibitor therapies. Thus, this study aimed to assess the role of adjuvant immune checkpoint inhibitor therapy for both renal cell carcinoma and urothelial carcinoma. A systematic review and network meta-analysis were conducted in compliance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. Multiple databases were searched for articles published as of February 2023. Studies were deemed eligible if they evaluated disease-free survival in patients with renal cell carcinoma and urothelial carcinoma receiving adjuvant immune checkpoint inhibitor therapy. Five studies met the inclusion criteria. In a network meta-analysis, pembrolizumab was shown to be the most effective regimen for patients with renal cell carcinoma, whereas nivolumab was found to be the most effective regimen for patients with urothelial carcinoma. Additionally, these results were consistently observed in a sub-analysis of the T stage. The present analysis provides findings that support the usefulness of adjuvant nivolumab therapy in urothelial carcinoma and adjuvant pembrolizumab therapy in renal cell carcinoma, in agreement with the currently available guidelines. However, the caveat is that the randomized controlled trials included in this analysis differed in important respects despite being similar in study design. Therefore, with these differences in mind, care needs to be taken when selecting patients for these immune checkpoint inhibitor therapies to maximize their benefits.

Challenges Coexist with Opportunities: Spatial Heterogeneity Expression of PD-L1 in Cancer Therapy

Cancer immunotherapy using anti-programmed death-ligand 1 (PD-L1) antibodies has been used in various clinical applications and achieved certain results. However, such limitations as autoimmunity, tumor hyperprogression, and overall low patient response rate impede its further clinical application. Mounting evidence has revealed that PD-L1 is not only present in tumor cell membrane but also in cytoplasm, exosome, or even nucleus. Among these, the dynamic and spatial heterogeneous expression of PD-L1 in tumors is mainly responsible for the unsatisfactory efficacy of PD-L1 antibodies. Hence, numerous studies focus on inhibiting or degrading PD-L1 to improve immune response, while a comprehensive understanding of the molecular mechanisms underlying spatial heterogeneity of PD-L1 can fundamentally transform the current status of PD-L1 antibodies in clinical development. Herein, the concept of spatial heterogeneous expression of PD-L1 is creatively introduced, encompassing the structure and biological functions of various kinds of PD-L1 (including mPD-L1, cPD-L1, nPD-L1, and exoPD-L1). Then an in-depth analysis of the regulatory mechanisms and potential therapeutic targets of PD-L1 is provided, seeking to offer a solid basis for future investigation. Moreover, the current status of agents is summarized, especially small molecular modulators development directed at these new targets, offering a novel perspective on potential PD-L1 therapeutics strategies.

Discovery of Novel PD-L1 Inhibitors That Induce the Dimerization, Internalization, and Degradation of PD-L1 Based on the Fragment Coupling Strategy

Tumor cells can evade immune surveillance through overexpressing programmed cell death-ligand 1 (PD-L1) to interact with programmed cell death-1 (PD-1). Besides, tumor-intrinsic PD-L1 is involved in tumor progression without interaction with PD-1, which provides more challenges for the discovery of PD-L1 inhibitors. Herein, we report the discovery of novel PD-L1 inhibitors using the fragment coupling strategy. Among them, B9 was found to inhibit the PD-1/PD-L1 interaction with the best IC50 value of 1.8 ± 0.7 nM. Beyond the blockade of the PD-1/PD-L1 axis, B9 promotes the dimerization, internalization, and degradation of PD-L1. Furthermore, B9 displayed high in vivo antitumor efficacy in the CT26 mouse model and activated the immune microenvironment and induced PD-L1 degradation of PD-L1 in the tumor. These results show that B9 is a promising lead PD-L1 inhibitor through the blockade of PD-1/PD-L1 interaction and functional inhibition of the PD-L1 signal pathway.

Trans-Regulation of Alternative PD-L1 mRNA Processing by CDK12 in Non-Small-Cell Lung Cancer Cells

Immunotherapy using checkpoint inhibitors targeting the interaction between PD-1 on T cells and PD-L1 on cancer cells has shown significant results in non-small-cell lung cancer (NSCLC). Not all patients respond to the therapy, and PD-L1 expression heterogeneity is proposed to be one determinant for this. The alternative processing of PD-L1 RNA, which depends on an alternative poly-A site in intron 4, generates a shorter mRNA variant (PD-L1v4) encoding soluble PD-L1 (sPD-L1), relative to the canonical PD-L1v1 mRNA encoding membrane-associated PD-L1 (mPD-L1). This study aimed to identify factors influencing the ratio between these two PD-L1 mRNAs in NSCLC cells. First, we verified the existence of the alternative PD-L1 RNA processing in NSCLC cells, and from in silico analyses, we identified a candidate list of regulatory factors. Examining selected candidates showed that CRISPR/Cas9-generated loss-of-function mutations in CDK12 increased the PD-L1v4/PD-L1v1 mRNA ratio and, accordingly, the sPD-L1/mPD-L1 balance. The CDK12/13 inhibitor THZ531 could also increase the PD-L1v4/PD-L1v1 mRNA ratio and impact the PD-L1 transcriptional response to IFN-γ stimulation. The fact that CDK12 regulates PD-L1 transcript variant formation in NSCLC cells is consistent with CDK12's role in promoting transcriptional elongation over intron-located poly-A sites. This study lays the groundwork for clinical investigations to delineate the implications of the CDK12-mediated balancing of sPD-L1 relative to mPD-L1 for immunotherapeutic responses in NSCLC.

Downregulation of osteoprotegerin in colorectal cancer cells promotes liver metastasis via activating tumor-associated macrophage

Osteoprotegerin (OPG) is a secreted cytokine that functions as a decoy receptor for receptor activator of nuclear factor kappa-B (RANK) ligand (RANKL). Anti-RANKL treatment for bone metastasis has been widely accepted for solid tumors. However, the mechanism of OPG-RANKL-RANK signaling in systemic colorectal cancer (CRC) metastasis remains unclear. In this study, we investigated the relevance and function of OPG expression in CRC liver metastasis. First, we performed in silico analysis using The Cancer Genome Atlas public database and found that lower OPG expression in CRC was associated with poor overall survival. Immunohistochemistry analyses using resected specimen from patients with CRC in our institute confirmed the result. Patient-matched primary CRC and liver metastases showed a significant downregulation of OPG expression in metastatic lesions. In CRC cell lines, OPG expression did not suppress cell proliferation and migration. However, OPG expression inhibited macrophage migration by suppressing the RANKL-RANK pathway. Moreover, in vivo mouse liver metastasis models showed that OPG expression in CRC cells suppressed liver metastases. In addition, treatment with an anti-RANKL neutralizing antibody also suppressed liver metastases. These results showed that downregulation of OPG expression in CRC cells promotes liver metastasis by activating tumor-associated macrophage, which can become a candidate for targeted therapy with anti-RANKL neutralizing antibody for CRC liver metastasis.

TIM-3 expression induces resistance to PD-1 inhibitor in G-CSF-producing lung spindle cell carcinoma: A case report

Lung spindle cell carcinoma is an aggressive subtype of pleomorphic lung cancer resistant to cytotoxic chemotherapy. Programmed cell death-1 (PD-1) inhibitors have been reported to have clinical effects in patients with spindle cell carcinoma; however, the resistance mechanism to PD-1 inhibitors is yet to be fully elucidated. Herein, we report the case of an 88-year-old man with G-CSF-producing spindle cell carcinoma who acquired resistance to PD-1/PD-ligand 1 (L1) inhibitor in an early setting after a remarkable response. A histopathological review of the resistant specimen revealed a low count of CD8+ T cells and a predominant presence of M2 and TIM-3+ macrophages, indicating the presence of an immunosuppressive microenvironment. Our findings suggest a novel resistance mechanism to PD-1/PD-L1 inhibitors in G-CSF-producing spindle cell carcinoma.

Identification of the functional PD-L1 interface region responsible for PD-1 binding and initiation of PD-1 signaling

The PD-1/PD-L1 checkpoint pathway is important for regulating immune responses and can be targeted by immunomodulatory drugs to treat a variety of immune disorders. However, the precise protein-protein interactions required for the initiation of PD-1/PD-L1 signaling are currently unknown. Previously, we designed a series of first-generation PD-1 targeting peptides based on the native interface region of programmed death ligand 1 (PD-L1) that effectively reduced PD-1/PD-L1 binding. In this work, we further characterized the previously identified lead peptide, MN1.1, to identify key PD-1 binding residues and design an optimized peptide, MN1.4. We show MN1.4 is significantly more stable than MN1.1 in serum and retains the ability to block PD-1/PD-L1 complex formation. We further characterized the immunomodulatory effects of MN1.4 treatment by measuring markers of T cell activation in a co-culture model with ovarian cancer cells and peripheral blood mononuclear cells. We found MN1.4 treatment reduced cytokine secretion and suppressed T cell responses in a similar manner as recombinant PD-L1. Therefore, the PD-L1 interface region used to design MN1.4 appeared sufficient to initiate PD-1 signaling and likely represents the minimum necessary region of PD-L1 required for PD-1 recognition. We propose a peptide agonist for PD-1, such as MN1.4, could have several applications for treating autoimmune disorders caused by PD-1 deficiencies such as type 1 diabetes, inflammatory arthritis, or autoimmune side effects arising from monoclonal antibody-based cancer immunotherapies.

Mediastinal lymph node removal modulates natural killer cell exhaustion in patients with non-small cell lung cancer

Non-small cell lung cancer (NSCLC) is the leading cause of cancer-related death globally. In this study, the effect of complete removal of mediastinal lymph nodes by video-assisted mediastinoscopic lymphadenectomy (VAMLA) on natural killer (NK) cell phenotype and functions in patients with NSCLC was evaluated. The study included 21 NSCLC patients (cIA-IVA) undergoing VAMLA staging and 33 healthy controls. Mononuclear cells were isolated from peripheral blood of all participants and mediastinal lymph nodes of the patients. NK cells were analyzed by flow cytometry to define NK subsets, expressions of PD-1, CTLA-4, activating/inhibitory receptors, granzyme A, and CD107a. The plasma levels of soluble PD-1, PDL-1, and CTLA-4 were measured by ELISA. Mediastinal lymph nodes of NSCLC patients had increased ratios of exhausted NK cells, increased expression of PD-1 and IL-10, and impaired cytotoxicity. Mediastinal lymph nodes removal increased CD56dimCD16bright cytotoxic effector phenotype and reduced exhausted NK cells. PD-1+ NK cells were significantly more abundant in patients' blood, and VAMLA significantly reduced their ratio as well. The ratio of IL-10 secreting regulatory NK cells was also reduced after VAMLA. Blood NK cells had increased cytotoxic functions and spontaneous IFN-γ secretion, and these NK cell functions were also recovered by VAMLA. Mediastinal lymph node removal reversed NK cell exhaustion, reduced regulatory NK cells, and improved antitumoral functions of NK cells. Tumor-draining lymph nodes may contribute to tumor evasion from antitumoral immune responses. The role of their removal needs to be further studied both to better understand this mechanism and as a potential immunotherapeutic approach.

The influence of plasma sPD-L1 concentration on the effectiveness of immunotherapy in advanced NSCLC patients

INTRODUCTION

PD-L1 (Programmed Cell Death Ligand 1) is currently the only recognised marker of response to immunotherapy with anti-PD-1 or anti-PD-L1 antibodies in patients with advanced non-small cell lung cancer (NSCLC). However, this marker is not perfect. Soluble PD-L1 (sPD-L1) may be a novel predictor of immunotherapy efficacy in NSCLC patients.

MATERIAL AND METHODS

We enrolled 120 patients (median age 68 ± 6.81 years, 70 males and 50 females) with locally advanced (stage IIIB; 10 patients) or advanced (stage IV; 110 patients) NSCLC. PD-L1 expression in tumour cells was assessed by immunohistochemistry (IHC) in 117 (97.5%) patients. The soluble PD-L1 concentration in plasma samples was measured using enzyme-linked immunosorbent assay (ELISA). The response to immunotherapy, progression-free survival (PFS), and overall survival (OS), calculated from the start of immunotherapy, were assessed in 119 patients.

RESULTS

Patients with disease control had significantly lower (p = 0.0006) concentrations of sPD-L1 in blood plasma than patients with progression during the first months of immunotherapy or chemoimmunotherapy Patients with ≥ 6 month progression-free survival had a significantly higher (p = 0.013) percentage of tumor cells with PD-L1 expression than patients with shorter PFS. Patients with ≥ 6 months OS had significantly lower (p = 0.0142) plasma sPD-L1 concentrations than those with shorter overall survival. The median PFS was significantly higher in patients with low sPD-L1 concentrations than in those with high concentrations of this protein (5.8 vs. 2.5 months, HR = 0.6021, p = 0.0156). Similarly, patients with low sPD-L1 levels had a significantly higher median overall survival than those with sPD-L1 levels above the median (16.5 vs. 7 months, HR = 0.5354, p = 0.0071). There was no significant correlation between the percentage of tumour cells expressing PD-L1 and the concentration of sPD-L1 in the blood plasma.

CONCLUSION

High sPD-L1 concentration is a negative predictor of immunotherapy efficacy in patients with NSCLC. It is worthwhile to determine sPD-L1 concentration to predict the risk of resistance to anti-PD-1 or anti-PD-L1 antibodies with greater certainty.

Targeting MS4A4A on tumour-associated macrophages restores CD8+ T-cell-mediated antitumour immunity

OBJECTIVE

Checkpoint immunotherapy unleashes T-cell control of tumours but is suppressed by immunosuppressive myeloid cells. The transmembrane protein MS4A4A is selectively highly expressed in tumour-associated macrophages (TAMs). Here, we aimed to reveal the role of MS4A4A+ TAMs in regulating the immune escape of tumour cells and to develop novel therapeutic strategies targeting TAMs to enhance the efficacy of immune checkpoint inhibitor (ICI) in colorectal cancer.

DESIGN

The inhibitory effect of MS4A4A blockade alone or combined with ICI treatment on tumour growth was assessed using murine subcutaneous tumour or orthotopic transplanted models. The effect of MS4A4A blockade on the tumour immune microenvironment was assessed by flow cytometry and mass cytometry. RNA sequencing and western blot analysis were used to further explore the molecular mechanism by which MS4A4A promoted macrophages M2 polarisation.

RESULTS

MS4A4A is selectively expressed by TAMs in different types of tumours, and was associated with adverse clinical outcome in patients with cancer. In vivo inhibition of MS4A4A and anti-MS4A4A monoclonal antibody treatment both curb tumour growth and improve the effect of ICI therapy. MS4A4A blockade treatment reshaped the tumour immune microenvironment, resulting in reducing the infiltration of M2-TAMs and exhausted T cells, and increasing the infiltration of effector CD8+ T cells. Anti-MS4A4A plus anti-programmed cell death protein 1 (PD-1) therapy remained effective in large, treatment-resistant tumours and could induce complete regression when further combined with radiotherapy. Mechanistically, MS4A4A promoted M2 polarisation of macrophages by activating PI3K/AKT pathway and JAK/STAT6 pathway.

CONCLUSION

Targeting MS4A4A could enhance the ICI efficacy and represent a new anticancer immunotherapy.

Decreased serum soluble programmed cell death ligand-1 level as a potential biomarker for missed miscarriage

STUDY QUESTION

Can maternal serum levels of soluble programmed cell death-1 (sPD-1) and its ligand (sPD-L1) serve as biomarkers for missed miscarriage (MM)?

SUMMARY ANSWER

Serum sPD-L1 levels are significantly decreased in MM patients and may serve as a potential predictive biomarker for miscarriage.

WHAT IS KNOWN ALREADY

Programmed cell death-1 (PD-1) and its ligand (PD-L1) comprise important immune inhibitory checkpoint signaling to maintain pregnancy. Their soluble forms are detectable in human circulation and are associated with immunosuppression.

STUDY DESIGN, SIZE, DURATION

Three independent cohorts attending tertiary referral hospitals were studied. The first (discovery) cohort was cross-sectional and included MM patients and healthy pregnant (HP) women matched on BMI. The second validation cohort contained MM patients and women with legally induced abortion (IA). The third prospective observational study recruited subjects requiring IVF treatment.

PARTICIPANTS/MATERIALS, SETTING, METHODS

In the discovery cohort, we enrolled 108 MM patients and 115 HP women who had a full-term pregnancy at 6-14 weeks of gestation. In the validation cohort, we recruited 25 MM patients and 25 women with IA. Blood samples were collected at the first prenatal visit for HP women or on the day of dilatation and curettage surgery (D&C) for MM and IA subjects to determine serum sPD-1 and sPD-L1 levels. Placenta samples were harvested during the D&C within the validation cohort to measure gene and protein expression. The prospective cohort collected serial blood samples weekly from 75 volunteers with embryo transfer (ET) after IVF.

MAIN RESULTS AND THE ROLE OF CHANCE

Circulating sPD-L1 levels were reduced by 50% in patients with MM (55.7 ± 16.04 pg/ml) compared to HP controls (106.7 ± 58.46 pg/ml, P < 0.001) and the difference remained significant after adjusting for maternal age and gestational age, whereas no significant differences in sPD-1 level were observed. Likewise, serum sPD-L1 was lower in MM patients than in IA subjects and accompanied by downregulated PD-L1-related gene expression levels in the placenta. In the IVF cohort, applying the changing rate of sPD-L1 level after ET achieved a predictive performance for miscarriage with receiver operating characteristics = 0.73 (95% CI: 0.57-0.88, P < 0.01).

LIMITATIONS, REASONS FOR CAUTION

The study was mainly confined to East Asian pregnant women. Further large prospective pregnancy cohorts are required to validate the predictive performance of sPD-L1 on miscarriage.

WIDER IMPLICATIONS OF THE FINDINGS

Reduced circulating sPD-L1 level and downregulated placental PD-L1 expression in miscarriage indicate that dysfunction in PD-L1 signals is a potential underlying mechanism for pregnancy loss. Our findings further extend the importance of the PD-L1 axis in pregnancy maintenance in early pregnancy.

STUDY FUNDING/COMPETING INTEREST(S)

This study was financially supported by grants from the Subject Innovation Team of Shaanxi University of Chinese Medicine (2019-Y502), General Research Fund (14122021), and Key Laboratory of Model Animal Phenotyping and Basic Research in Metabolic Diseases (2018KSYS003). The authors declare that they have no competing interests to be disclosed.

TRIAL REGISTRATION NUMBER

N/A.

Soluble PD-L1 as a diagnostic and prognostic biomarker in resectable gastric cancer patients

BACKGROUND

In this study, we compared programmed death-ligand 1 (PD-L1) expression in primary tissue samples and its soluble form (sPD-L1) concentration in matched preoperative plasma samples from gastric cancer patients to understand the relationship between tissue and plasma PD-L1 expression and to determine its diagnostic and prognostic value.

METHODS

PD-L1 expression in tissue was assessed by immunohistochemistry and enzyme-linked immunosorbent assay (ELISA), and sPD-L1 concentration in plasma was quantified by ELISA. The levels of the CD274 gene, which encodes for PD-L1 protein, were examined as part of bulk tissue RNA-sequencing analyses. Additionally, we evaluated the association between sPD-L1 levels and various laboratory parameters, disease characteristics, and patient outcomes.

RESULTS

GC patients had significantly higher levels of sPD-L1 in their plasma (71.69 pg/mL) compared to healthy controls (35.34 pg/mL) (p < 0.0001). Moreover, sPD-L1 levels were significantly correlated with tissue PD-L1 protein, CD274 mRNA expression, larger tumor size, advanced tumor stage, and lymph node metastasis. Elevated sPD-L1 levels (> 103.5 ng/mL) were associated with poor overall survival (HR = 2.16, 95%CI 1.15-4.08, p = 0.017). Furthermore, intratumoral neutrophil and dendritic cell levels were directly correlated with plasma sPD-L1 concentration in the GC patients.

CONCLUSIONS

sPD-L1 was readily measurable in GC patients, and its level was associated with GC tissue PD-L1 expression, greater inflammatory cell infiltration, disease progression, and survival. Thus, sPD-L1 may be a useful minimally invasive diagnostic and prognostic biomarker in GC patients.

Progresses in biomarkers for cancer immunotherapy

Currently, checkpoint inhibitor-based immunotherapy has emerged as prevailing treatment modality for diverse cancers. However, immunotherapy as a first-line therapy has not consistently yielded durable responses. Moreover, the risk of immune-related adverse events increases with combination regimens. Thus, the development of predictive biomarkers is needed to optimize individuals benefit, minimize risk of toxicities, and guide combination approaches. The greatest focus has been on tumor programmed cell death-ligand 1 (PD-L1), microsatellite instability (MSI), and tumor mutational burden (TMB). However, there remains a subject of debate due to thresholds variability and significant heterogeneity. Major unmet challenges in immunotherapy are the discovery and validation of predictive biomarkers. Here, we show the status of tumor PD-L1, MSI, TMB, and emerging data on novel biomarker strategies with oncogenic signaling and epigenetic regulation. Considering the exploration of peripheral and intestinal immunity has served as noninvasive alternative in predicting immunotherapy, this review also summarizes current data in systemic immunity, encompassing solute PD-L1 and TMB, circulating tumor DNA and infiltrating lymphocytes, routine emerging inflammatory markers and cytokines, as well as gut microbiota. This review provides up-to-date information on the evolving field of currently available biomarkers in predicting immunotherapy. Future exploration of novel biomarkers is warranted.

RNA splicing alterations in lung cancer pathogenesis and therapy

RNA splicing alterations are widespread and play critical roles in cancer pathogenesis and therapy. Lung cancer is highly heterogeneous and causes the most cancer-related deaths worldwide. Large-scale multi-omics studies have not only characterized the mutational landscapes but also discovered a plethora of transcriptional and post-transcriptional changes in lung cancer. Such resources have greatly facilitated the development of new diagnostic markers and therapeutic options over the past two decades. Intriguingly, altered RNA splicing has emerged as an important molecular feature and therapeutic target of lung cancer. In this review, we provide a brief overview of splicing dysregulation in lung cancer and summarize the recent progress on key splicing events and splicing factors that contribute to lung cancer pathogenesis. Moreover, we describe the general strategies targeting splicing alterations in lung cancer and highlight the potential of combining splicing modulation with currently approved therapies to combat this deadly disease. This review provides new mechanistic and therapeutic insights into splicing dysregulation in cancer.

PD-L1 positive astrocytes attenuate inflammatory functions of PD-1 positive microglia in models of autoimmune neuroinflammation

Multiple Sclerosis (MS) is a chronic autoimmune inflammatory disorder of the central nervous system (CNS). Current therapies mainly target inflammatory processes during acute stages, but effective treatments for progressive MS are limited. In this context, astrocytes have gained increasing attention as they have the capacity to drive, but also suppress tissue-degeneration. Here we show that astrocytes upregulate the immunomodulatory checkpoint molecule PD-L1 during acute autoimmune CNS inflammation in response to aryl hydrocarbon receptor and interferon signaling. Using CRISPR-Cas9 genetic perturbation in combination with small-molecule and antibody-mediated inhibition of PD-L1 and PD-1 both in vivo and in vitro, we demonstrate that astrocytic PD-L1 and its interaction with microglial PD-1 is required for the attenuation of autoimmune CNS inflammation in acute and progressive stages in a mouse model of MS. Our findings suggest the glial PD-L1/PD-1 axis as a potential therapeutic target for both acute and progressive MS stages.

Meta-analysis of the prognostic value of soluble programmed death ligand-1 (sPD-L1) in cancers

BACKGROUND

The soluble programmed death ligand-1 (sPD-L1) and its prognostic role in cancers have been investigated in numerous studies. However, due to the inconsistency on some findings, this meta-analysis was performed to assess the prognostic value of sPD-L1 in patients with cancer.

METHODS

We searched the PubMed, Web of Science, MEDLINE, Wiley Online Library and ScienceDirect, and screened the studies for eligibility. Recurrence-free survival (RFS), progression-free survival (PFS) and disease-free survival (DFS) were for short term survival. The overall survival (OS) was for long term survival.

RESULTS

Forty studies with 4441 patients were included in this meta-analysis. Elevated sPD-L1 was associated with short OS [HR = 2.44 (2.03-2.94), p = 0.000]. Moreover, a high sPD-L1 was predictive of worse DFS/RFS/PFS [HR = 2.52 (1.83-3.44), p = 0.000]. In addition, high sPD-L1 was consistently correlated with poor OS in irrespective of study type, univariate and multivariate analysis, ethnicity, cut-off value of sPD-L1, sample and treatment. In the subgroup analysis, high sPD-L1 was correlated with poor OS in gastrointestinal cancer, lung cancer, hepatic cancer, oesophageal cancer and clear cell renal cell carcinoma.

CONCLUSIONS

The present meta-analysis showed that a high level of sPD-L1 was associated with worse prognosis in some types of cancer.

Function and clinical application of exosome-how to improve tumor immunotherapy?

In recent years, immunotherapy has been increasingly used in clinical practice to treat tumors. However, immunotherapy's efficacy varies between tumor types and patient populations, and long-term drug resistance often occurs during treatment. Therefore, it is essential to explore the molecular mechanisms of immunotherapy to improve its efficacy. In this review, we focus on the significance of tumor-derived exosomes in the clinical treatment of tumors and how modifying these exosomes may enhance immune effectiveness. Specifically, we discuss exosome components, such as RNA, lipids, and proteins, and the role of membrane molecules on exosome surfaces. Additionally, we highlight the importance of engineered exosomes for tumor immunotherapy. Our goal is to propose new strategies to improve the efficacy of tumor immunotherapy.

Mechanical force regulates ligand binding and function of PD-1

Immune checkpoint blockade targeting PD-1 shows great success in cancer therapy. However, the mechanism of how ligand binding initiates PD-1 signaling remains unclear. As prognosis markers of multiple cancers, soluble PD-L1 is found in patient sera and can bind PD-1, but fails to suppress T cell function. This and our previous observations that T cells exert endogenous forces on PD-1-PD-L2 bonds prompt the hypothesis that mechanical force might be critical to PD-1 triggering, which is missing in the soluble ligand case due to the lack of mechanical support afforded by surface-anchored ligand. Here we show that PD-1 function is eliminated or reduced when mechanical support on ligand is removed or dampened, respectively. Force spectroscopic analysis reveals that PD-1 forms catch bonds with both PD-Ligands <7 pN where force prolongs bond lifetime, but slip bonds >8 pN where force accelerates dissociation. Steered molecular dynamics finds PD-1-PD-L2 complex very sensitive to force due to the two molecules' "side-to-side" binding via β sheets. Pulling causes relative rotation and translation between the two molecules by stretching and aligning the complex along the force direction, yielding new atomic contacts not observed in the crystal structure. Compared to wild-type, PD-1 mutants targeting the force-induced new interactions maintain the same binding affinity but display lower rupture force, shorter bond lifetime, reduced tension, and most importantly, impaired capacity to suppress T cell activation. Our results uncover a mechanism for cells to probe the mechanical support of PD-1-PD-Ligand bonds using endogenous forces to regulate PD-1 triggering.

Immunomodulatory Gene-Splicing Dysregulation in Tumorigenesis: Unmasking the Complexity

Cancer is a global health concern with rising incidence, morbidity, and mortality. The interaction between the tumor and immune cells within the tumor microenvironment is facilitated by signaling pathways driven by immunomodulatory proteins. Alternative splicing regulates the production of multiple immunomodulatory proteins with diverse functionality from a single mRNA transcript. Splicing factors are pivotal in modulating alternative splicing processes but are also subject to regulation. The dysregulation of alternative splicing may result from splicing factor (SF) abnormal expression levels and mutations in the cis and trans-acting elements and small nuclear RNA (snRNA) molecules. Aberrant splicing may generate abnormal mRNA transcripts encoding isoforms with altered functions that contribute to tumorigenesis or cancer progression. This review uncovers the complexity of immunomodulatory genes splicing dysregulation in oncogenesis. Identifying specific immunomodulatory splicing isoforms that contribute to cancer could be utilized to improve current immunotherapeutic drugs or develop novel therapeutic interventions for cancer.

Targeting alternative splicing in cancer immunotherapy

Tumor immunotherapy has made great progress in cancer treatment but still faces several challenges, such as a limited number of targetable antigens and varying responses among patients. Alternative splicing (AS) is an essential process for the maturation of nearly all mammalian mRNAs. Recent studies show that AS contributes to expanding cancer-specific antigens and modulating immunogenicity, making it a promising solution to the above challenges. The organoid technology preserves the individual immune microenvironment and reduces the time/economic costs of the experiment model, facilitating the development of splicing-based immunotherapy. Here, we summarize three critical roles of AS in immunotherapy: resources for generating neoantigens, targets for immune-therapeutic modulation, and biomarkers to guide immunotherapy options. Subsequently, we highlight the benefits of adopting organoids to develop AS-based immunotherapies. Finally, we discuss the current challenges in studying AS-based immunotherapy in terms of existing bioinformatics algorithms and biological technologies.