Exosomal Programmed Death-ligand 1 Research Articles

The role of programmed death receptor (PD-)1/PD-ligand (L)1 in periodontitis and cancer.

The programmed-death-ligand-1 (PD-L1) is an immune-modulating molecule that is constitutively expressed on various immune cells, different epithelial cells and a multitude of cancer cells. It is a costimulatory molecule that may impair T-cell mediated immune response. Ligation to the programmed-death-receptor (PD)-1, on activated T-cells and further triggering of the related signaling pathways can induce T-cells apoptosis or anergy. The upregulation of PD-L1 in various cancer types, including oral squamous cell carcinomas, was demonstrated and has been linked to immune escape of tumors and poor prognosis. A bidirectional relationship exists between the increased PD-L1 expression and periodontitis as well as the epithelial-mesenchymal transition (EMT), a process of interconversion of epithelial cells to mesenchymal cells that may induce immune escape of tumors. Interaction between exosomal PD-L1 and PD-1 on T-cells may cause immunosuppression by blocking the activation and proliferation of T-cells. The efficacy and importance of treatment with PD-1/PD-L1 checkpoint inhibitors and their prognostic influence on human cancers was demonstrated. Regarding PD-1/PD-L1 checkpoint inhibitors, resistances exist or may develop, basing on various factors. Further investigations of the underlying mechanisms will help to overcome the therapeutic limitations that result from resistances and to develop new strategies for the treatment of cancer.

Coaxial dual-path electrochemical biosensing and logic strategy-based detection of lung cancer-derived exosomal PD-L1.

Exosomal programmed death ligand-1 (ExoPD-L1) is a vital marker of immune activation in the early stages of tumor therapy and it can inhibit anti-tumor immune responses. However, due to the low expression of ExoPD-L1 in cancer cells, it is difficult to perform highly sensitive assays and accurately differentiate cancer sources. Therefore, we constructed a coaxial dual-path electrochemical biosensor for highly accurate identification and detection of ExoPD-L1 from lung cancer based on chemical-biological coaxial nanomaterials and nucleic acid molecular signal amplification strategies. The measurements showed that the detected ExoPD-L1 concentrations ranged from 6 × 102 particles per mL to 6 × 108 particles per mL, and the detection limit was 310 particles per mL. Compared to other sensors, the electrochemical biosensor designed in this study has a lower detection limit and a wider detection range. Furthermore, we also successfully identified lung cancer-derived ExoPD-L1 by analyzing multiple protein biomarkers expressed on exosomes through the "AND" logic strategy. This sensor platform is expected to realize highly sensitive detection and accurate analysis of multiple sources of ExoPD-L1 and provide ideas for the clinical detection of ExoPD-L1.

The Predictive Value of Circulating Exosomal PD-L1 in Cervical Cancer Immunotherapy

Programmed death ligand 1 (PD-L1) expression was wildly used as a predictor of immune Check-Point Inhibitors (ICIs) efficiency. However, emerging results showed that PD-L1 was of great heterogeneity in sampling time and site. Recently, some studies found that exosomal PD-L1(ExoPD-L1) was related to ICIs response. In this study, we aimed to explore the predictive value of ExoPD-L1 in ICIs treatment of cervical cancer (CC) for the first time. A total of 40 primarily diagnosed CC patients who accepted radical radiotherapy (RT) from March 2021 to October 2022 were included. The consecutive tumor sample were collected before and during RT. Another 37 advanced CC patients who accepted ICIs combination therapy from June 2020 to October 2022 were enrolled in this study. Blood samples were collected from each participant before and during treatment. Exosomes were derived by differential centrifugation, which was further identified by Western blot (WB) (CD9/TSG101/Calnexin), transmission electron microscope analysis and nanoparticle tracking analysis. ExoPD-L1 detection was conducted by enzyme-linked immuno-sorbent assay (ELISA). The knockout of PD-L1 was conducted via CRISPR/Cas9 assay and the overexpress of PD-L1 was conducted by lentiviral transfection. CD8+ T cells were extracted from murine spleen by CD8+ T Cell Isolation Kit. Immune cells and cytokines markers were detected by multicolor flow cytometry. The consecutive detection of PD-L1 showed a dynamic change during RT. Compared with the level before RT, PD-L1 expression elevated in most patients (87.5%, 35/40) after RT. And the responders (n = 18) had elevated ExoPD-L1 level at the first two circles in the ICIs combination therapy (P<0.001). Whereas the level of pre-treatment ExoPD-L1 couldn't stratified clinical responders and non-responders (P = 0.181). The median follow-up time was 14.13 months. The mPFS in increased group vs. decreased group: not reach vs.11.02 months (P = 0.025, HR: 0.218, 0.052-0.913). Continuous blood sampling of mice models also found that effective therapeutic intervention could increase ExoPD-L1 in the early stage. The combination of exosome inhibitor GW4869 and anti-PD-1 further inhibited tumor growth. Mice were injected with external ExoPD-L1OE and ExoPD-L1KO. The results showed that ExoPD-L1OE suppressed body immunity and promoted tumor growth. The results of flow cytometry showed that ExoPD-L1OE inhibited CD8+ T cells from releasing interferon-and granzyme B. And ExoPD-L1OE also suppressed the CD8+ T cells proliferation in murine spleen. The coculture of CD8+ T cells and exosomes in vitro also confirmed the above conclusion. Compared with unstable and impressionable tumoral PD-L1, ExoPD-L1 seems to be better predictor for the efficacy of immunotherapy in CC, which was with easy accessibility and continuation. Exosome PD-L1 played an immunosuppressive role by inhibiting the proliferation and functional factor release of CD8+ T cell.

Comprehensive Detection of PD-L1 Protein and mRNA in Tumor Cells and Extracellular Vesicles through a Real-Time qPCR Assay.

A growing number of studies have shown that tumor cells secrete extracellular vesicles (EVs) containing programmed death-ligand 1 (PD-L1) protein. These vesicles can travel to lymph nodes and remotely inactivate T cells, thereby evading immune system attack. Therefore, the simultaneous detection of PD-L1 protein expression in cells and EVs is of great significance in guiding immunotherapy. Herein, we developed a method based on qPCR for the simultaneous detection of PD-L1 protein and mRNA in EVs and their parental cells (PREC-qPCR assay). Lipid probes immobilized on magnetic beads were used to capture EVs directly from samples. For RNA assay, EVs were directly broken by heating and quantified with qPCR. As to protein assay, EVs were recognized and bound with specific probes (such as aptamers), which were used as templates in subsequent qPCR analysis. This method was used to analyze EVs of patient-derived tumor clusters (PTCs) and plasma samples from patients and healthy volunteers. The results revealed that the expression of exosomal PD-L1 in PTCs was correlated with tumor types and significantly higher in plasma-derived EVs from tumor patients than that of healthy individuals. When extended to cells and PD-L1 mRNAs, the results showed that the expression of PD-L1 protein was consistent with mRNA in cancer cell lines, while PTCs demonstrated significant heterogeneity. This comprehensive detection of PD-L1 at four levels (cell, EVs, protein, and mRNA) is believed to enhance our understanding of the relationship among PD-L1, tumors, and the immune system and to provide a promising tool for predicting the benefits of immunotherapy.

Circulating exosomal PD-L1 to predict response with immunotherapy in patients with advanced cervical cancer.

e17514 Background: Programmed death ligand 1 (PD-L1) expression was wildly used to predict immune Check-Point Inhibitors (ICIs) efficiency. However, emerging results showed that PD-L1 was of great heterogeneity in sampling time and site. Recently, some studies found that exosomal PD-L1(ExoPD-L1) was related to ICIs response. In this study, we aimed to explore the predictive value of ExoPD-L1 in ICIs treatment of cervical cancer (CC) for the first time. Methods: 40 primarily diagnosed CC patients who accepted radical radiotherapy (RT) were included. The consecutive tumor sample were collected before and during RT. Another 37 advanced CC patients who accepted ICIs combination therapy were collected. Blood samples were collected from each participant before and during treatment. Exosomes were derived by differential centrifugation, which was further identified by Western blot (CD9/TSG101/Calnexin), transmission electron microscope analysis and nanoparticle tracking analysis. ExoPD-L1 detection was conducted by enzyme-linked immuno-sorbent assay (ELISA). The knockout of PD-L1 was conducted via CRISPR/Cas9 assay and the overexpress of PD-L1 was conducted by lentiviral transfection. CD8+ T cells were extracted from murine spleen by CD8+ T Cell Isolation Kit. Immune cells and cytokines markers were detected by multicolor flow cytometry. Results: The consecutive detection of PD-L1 showed a dynamic change during RT. Compared with the level before RT, PD-L1 expression elevated in most patients (87.5%, 35/40) after RT. And the responders (n = 18) had elevated ExoPD-L1 level at the first two circles in the ICIs combination therapy (P &lt; 0.001). Whereas the level of pre-treatment ExoPD-L1 couldn’t stratified clinical responders and non-responders (P = 0.181). The median follow-up time was 14.13 months. The mPFS in increased group vs. decreased group: not reach vs.11.02 months (P = 0.025, HR: 0.218, 0.052-0.913). Continuous blood sampling of mice models also found that effective therapeutic intervention could increase ExoPD-L1 in the early stage. The combination of exosome inhibitor GW4869 and anti-PD-1 further inhibited tumor growth. Mice were injected with external ExoPD-L1OE and ExoPD-L1KO. The results showed that ExoPD-L1OE suppressed body immunity and promoted tumor growth. The results of flow cytometry showed that ExoPD-L1OE inhibited CD8+ T cells from releasing interferon-γand granzyme B. And ExoPD-L1OE also suppressed the CD8+ T cells proliferation in murine spleen. The coculture of CD8+ T cells and exosomes in vitro also confirmed the above conclusion. Conclusions: Compared with unstable and impressionable tumoral PD-L1, ExoPD-L1 seems to be better predictor for the efficacy of immunotherapy in CC, which was with easy accessibility and continuation. Exosome PD-L1 played an immunosuppressive role by inhibiting the proliferation and functional factor release of CD8+ T cell.

Assembly of Nanocatalyst As a Noninvasive Tool for Breast Cancer Diagnosis and Immunotherapy Surveillance Designed by Visually Tracking Tumor-Derived Exosomal PD-L1

Immunotherapy has reshaped the therapeutic landscape of many advanced tumors; however, its effectiveness is seriously hampered due to the limitations of existing predictors and diagnostic tools. In response, we have fabricated a noninvasive tool for the diagnosis and immunotherapy surveillance of breast cancer (BC). The diagnostic tool functions by performing dual-aptamer-activated tandem assembly of a nanocatalyst for visually tracking tumor-derived exosomal programmed death-ligand 1 (PD-L1). By accurately identifying serum exosomal PD-L1 derived from BC, the diagnostic tool can rival immunohistochemistry (IHC) in the early classification of PD-L1-positive groups, PD-L1-negative groups, and healthy donors. Furthermore, real-time monitoring of the response to immunotherapy in 6 BC patients treated with anti-PD-L1 antibodies has been successfully achieved with the naked eye or a mobile phone camera by virtue of this diagnostic tool, which is highly consistent with computed tomography. Together, our work offers an unprecedented diagnostic tool for identifying potential beneficiaries and monitoring the response to immunotherapy, which highlights the significance of exosomal PD-L1 derived from tumors as a potential tumor prognostic and diagnostic factor including but not limited to BC.

Extracellular vesicle-based checkpoint regulation and immune state in cancer.

Tumor cells exploit several mechanisms for hijacking an immunosuppressive tumor ecosystem in order to evade immune surveillance and to progress toward metastasis. Equipment of extracellular vesicles (EVs) with checkpoints is an example of cancer control over anti-tumor responses from immune system. Programmed death-ligand 1 (PD-L1) is a checkpoint highly expressed in a tumor at progressive stage. Interactions between PD-L1 with its receptor programmed death-1 receptor (PD-1) expressed on T cells will block the effector function of CD8+ T cells, known as one of the most important defensive cells against cancer. Evaluation of circulatory exosomal PD-L1 can be a prognostic biomarker in tumor diagnosis and responses to the immune checkpoint inhibitor (ICI) therapy, and can be considered as a tool in clinical practice for exploiting personalized therapy. Cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) is also a checkpoint that its engagement with CD80/CD86 expressed on antigen-presenting cells (APCs), such as dendritic cells (DCs) hamper the priming phase of CD4+ and CD8+ T cells. Harvesting EVs from tumor and their modification with desired anti-checkpoint antibodies can be a promising strategy in cancer immunotherapy. The aim of this review is to discuss about EV roles in checkpoint regulation, cancer diagnosis and ICI responses, and to survey possible application of such vesicles in cancer immunotherapy.

Simultaneous detection of cancerous exosomal miRNA-21 and PD-L1 with a sensitive dual-cycling nanoprobe

Simultaneous detection of specific exosomal surface proteins and inner microRNAs are hampered by their heterogeneity, low abundance and spatial segregation in nanovesicles. Here, we design a dual-cycling nanoprobe (DCNP) to enable single-step simultaneous quantitation of cancerous exosomal surface programmed death-ligand 1 (PD-L1) (ExoPD-L1) and miRNA-21 (ExomiR-21) directly in exosome lysates, without resorting to either RNA extraction or time-consuming transmembrane penetration. In this design, DNA molecular machine-based dual-recognition probes co-assemble onto gold nanoparticle surface for engineering ‘silent’ DCNPs, which enable signal-amplified synchronous response to dual-targets as activated by ExomiR-21 and ExoPD-L1 within 20 min. Benefiting from cycling amplification of the molecular machine, DCNPs sensor achieves detection limits of tumor exosomes, ExoPD-L1 and ExomiR-21 down to 10 particles/μL, 0.17 pg/mL and 66 fM, respectively. Such a sensitive dual-response strategy allows simultaneous tracking the dynamic changes of ExoPD-L1 and ExomiR-21 expression regulated by signaling molecules or therapeutics. This approach further detects circulating ExoPD-L1 and ExomiR-21 in human plasma to differentiate breast cancer patients from healthy individuals with high accuracy, showing great potential of DCNPs for simultaneous profiling exosomal surface and inside biomarkers, and for clinical precision diagnosis.

Abstract 1345: p300/CBP bromodomain inhibitor CCS1477 enhances the efficacy of immune checkpoint blockade therapy in cancer treatment

Abstract Background: Blockade of programmed death-ligand 1 (PD-L1) by therapeutic antibodies has shown to be a promising strategy in cancer therapy, yet clinical response in many types of cancer is limited. Tumor cells secrete PD-L1 through exosomes or splice variants, which has been described as a new mechanism for the resistance to PD-L1 blockade therapy in multiple cancers. Our previous findings showed that the histone acetyltransferases p300/CBP could be recruited to the promoter of CD274 (encoding PD-L1) to regulate the expression of PD-L1. P300/CBP inhibition abrogated this process and reduced the secretion of exosomal PD-L1 by blocking the transcription of CD274, which combined with the anti-PD-L1 antibody to reactivate T cells function for tumor attack. In this study we have tested the outcome of combined immune checkpoint inhibitors with CCS1477, a novel p300/CBP bromodomain inhibitor, in pre-clinical models of prostate cancer and melanoma. Results: CCS1477 significantly decreased human prostate (DU145/PC-3) and melanoma (A375/SK-MEL-28) cancer cell line PD-L1 expression, as well as exosome secreted PD-L1 after 24 hours treatment. Moreover, consistent with these findings in vitro, CCS1477 (2.5mg//kg) also reduced PD-L1 expression in a syngeneic mouse prostate model (TRAMP-C2) and syngeneic mouse melanoma model (B16-F10). Meanwhile, CCS1477 treatment significantly increased tumor-infiltrating CD8+ and CD4+ T cells in syngeneic mouse models. Monotherapy treatment with CCS1477 or immune checkpoint inhibitors (anti-PD-L1 antibody for prostate cancer or anti-PD-L1 and anti-CTLA4 antibody for melanoma) resulted in significant but modest efficacy. Strikingly, the combination of immune checkpoint inhibitors with CCS1477 showed robust synergistic responses resulting in tumor regression. Mechanistically, CCS1477 treatment induced significant loss of H3K27 acetylation from super-enhancers of CD274, which subsequently induced a significant reduction of PD-L1 expression and exosome secreted-PD-L1. Also, we found that CCS1477 treatment significantly decreased the abundance of circulating and tumor-infiltrating myeloid-derived suppressor cells (MDSCs), which are known to play important roles in tumor immune evasion by inhibiting T cell’s activation. Reduction of MDSCs and exosome secreted-PD-L1 preserved T-cell function and elicited robust immunotherapy response combined with immune checkpoint blockade agents. Conclusions: These observations illuminate a clinically relevant hypothesis for combining CCS1477 with immune checkpoint blockade in the treatment of cancer. Citation Format: Jinghui Liu, Xinyi Wang, Katelyn Jones, Nigel Brooks, Neil Pegg, Xiaoqi Liu. p300/CBP bromodomain inhibitor CCS1477 enhances the efficacy of immune checkpoint blockade therapy in cancer treatment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1345.

High exosomal PD-L1 expression in relation to lymph node progression in metastatic castration-resistant prostate cancer (mCRPC) treated with abiraterone (abi) or enzalutamide (enza).

e17038 Background: Programmed death-ligand 1 (PD-L1) has been recently found in tumor-derived exosomes and associated with progressive disease (PD) ( Poggio, Cell 2019). In localized prostate cancer, PD-L1 tumor expression has been shown to be a biomarker for node-positive patients (pts) ( Petitprez, Eur Urol Focus 2019) but its role in mCRPC is largely unexplored. We aimed to determine the potential of PD-L1 exosomal expression to predict lymph nodal PD in mCRPC receiving abi or enza. Methods: In a biomarker prospective study (REC 2192/2013), exosomes were isolated from plasma samples collected before first-line therapy with abi/enza between December 2014 and October 2018. RNA was extracted for analysis of PD-L1 by digital droplet PCR ( Del Re, Prostate Cancer Prostatic Dis 2021). Results: In our cohort of 55 node-positive mCRPC pts (median age: 76 years, range 47-89), the amount of exosomal PD-L1 expression (pts dichotomized in “high” and “low” as below or above median PD-L1/ACTB ratio = 0.0052) was associated with radiographic response after the first 3 months abi/enza therapy [high PD-L1 vs low PD-L1: 8 (25.8%) vs 0 (0%) PD, 23 (74.2%) vs 18 (75%) stable disease, and 0 vs 6 (25%) partial/complete response] (p = 0.0009). We observed an overall median progression-free survival (PFS) of 14.3 months [95% confidence interval (CI) 8.6-not reached] shorter in high PD-L1 compared to low PD-L1 10.6 (6.5-23.4) vs not reached [hazard ratio (HR) 3.1 (95% CI 1.1-8.5), p = 0.023]. In multivariable analysis including exosomal PD-L1 and androgen receptor (AR) variant 7, AR copy number gain detected in plasma, neutrophil lymphocyte ratio (NLR), lactate dehydrogenase, exosomal PD-L1; AR-V7 and AR gain were independent predictors of nodal PFS (HR 5.8, 95% CI 1.4-24.2, p = 0.01, HR 3.2, 95% CI 1.1-9.2, p = 0.03 and HR 12.9, 95% CI 2.3-73.2, p = 0.004), whereas AR-V7, AR gain, NLR &gt; 3 were independent predictors of OS (HR 4.9, 95% CI 1.8-13.1, p = 0.001, HR 4.4, 95% CI 1.1-17, p = 0.02, and HR 3.2 95% CI 1.1-9.4, p = 0.03, respectively). Moreover, a trend of a worse OS was reported in high PD-L1 compared to low PD-L1 pts (HR 2.6, 95% CI 0.9-7.5, p = 0.07). Conclusions: In mCRPC pts treated with ARSI, exosomal PD-L1 expression may be considered as a predictive biomarker of lymph nodal response, playing a potential role in individualized disease monitoring and treatment combining between ARSI and immunotherapy. Larger evaluation of treatment decisions based on exosomal PD-L1 expression is now required.

Antitumor activity of bintrafusp alfa in previously treated patients with recurrent or metastatic nasopharyngeal cancer (NPC): A single arm, prospective phase II trial.

e18029 Background: Patients with recurrent or metastatic nasopharyngeal cancer (R/M NPC) who failed platinum-based chemotherapy have poor prognoses. We report the clinical activity and safety of bintrafusp alfa, a first-in-class bifunctional fusion protein composed of the extracellular domain of the transforming growth factor (TGF)-βRII receptor fused to a human IgG1 antibody blocking programmed death-ligand 1 (PD-L1), in patients with heavily pretreated R/M NPC. Tumor and plasma-based biomarkers were investigated in an exploratory analysis. Methods: Eligible patients had histologically confirmed NPC that had recurred at distant sites and were not amenable to curative treatment. All patients received at least one prior line of platinum-based chemotherapy for recurrent disease. Patients were treated with bintrafusp alfa (1200mg every 2 weeks) until disease progression. The sample size was estimated to assume a 40% objective response rate (ORR) to bintrafusp alfa compared with 20% for checkpoint inhibitors. Modified Simon two-stage optimal design was used (power, 80%; a = 0.05; P0 = 0.20; P1 = 0.40; n1 = 18; n = 33 with an additional five patients to allow for ineligibility or other reasons). The primary endpoint was ORR and secondary endpoints included survival and toxicity. Expression of PD-L1 in archived tumors, plasma clearance of Epstein-Barr virus (EBV) DNA, plasma clearance of TGF-β, and exosomal PD-L1 were assessed for a potential correlation with ORR. (NCT 04396886). Results: Out of 43 patients screened, 38 patients were enrolled. After a median follow-up of 14.9 months (range: 1.6-23.3 months), the confirmed ORR was 23.7% (95% CI: 12.4-38.8%) (complete response, n = 1; partial response, n = 8). The median treatment duration was 1.8 months (range: 0.5-14.3 months). 8 patients (21.1%) and 2 patients (5.3%) received bintrafusp alfa for &gt; 6 months and &gt; 12 months respectively. The 1-year overall survival (OS) rate was 57.5% (95% CI, 40.2% to 71.5%) and 1-year progression-free survival rate was 23% (95% CI, 10.1% to 39.4%). ORR was higher in patients with a decreasing trend in EBV-DNA at week 4 (40% vs. 6.3%, p = 0.02), whereas high exosomal PD-L1 levels at week 4 were predictive of worse ORR (5.3% vs. 41.7%, p = 0.012). There were no associations between clinical outcome and tissue PD-L1 expression (p = 0.952) or plasma TGF-β clearance (p = 0.28). 16 patients (42.4%) experienced ≥ grade 3 treatment-related adverse events, most commonly anemia (n = 9, 23.7%) and secondary malignancies (n = 4, 10.5%). Conclusions: Bintrafusp alfa has promising activity in heavily pretreated R/M NPC and a favorable 1-year OS rate, though the observed activity was not as high as the study initially aimed. The biomarker results warrant validation in larger cohorts. Clinical trial information: NCT04396886.

Exosomal CD73 from serum of patients with melanoma suppresses lymphocyte functions and is associated with therapy resistance to anti-PD-1 agents

BackgroundCD73 is an ectonucleotidase producing the immunosuppressor mediator adenosine. Elevated levels of circulating CD73 in patients with cancer have been associated with disease progression and poor response to immunotherapy. Immunosuppressive...

GOLM1 exacerbates CD8+ T cell suppression in hepatocellular carcinoma by promoting exosomal PD-L1 transport into tumor-associated macrophages

The immunosuppressive microenvironment plays an important role in tumor progression and immunotherapy responses. Golgi membrane protein 1 (GOLM1) is correlated to hepatocellular carcinoma (HCC) progression and metastasis. However, little is known about the role of GOLM1 in regulating the immunosuppressive environment and its impact on immunotherapeutic efficacy in HCC. In this study, GOLM1 was positively correlated with infiltrating tumor-associated macrophages (TAMs) expressed high levels of programmed death-ligand 1 (PD-L1) and CD8+ T cell suppression in HCC tissues. Both gain- and loss-of-function studies determined a close correlation between GOLM1 and immunosuppression. In the mechanism, GOLM1 promoted COP9 signalosome 5-mediated PD-L1 deubiquitination in HCC cells and increased the transport of PD-L1 into exosomes via suppression of Rab27b expression. Furthermore, co-culture with exosomes derived from HCC cells upregulated the expression of PD-L1 on macrophages. Zoledronic acid in combination with anti-PD-L1 therapy reduced PD-L1+ TAMs infiltration and alleviated CD8+ T cell suppression, resulting in tumor growth inhibition in the mouse HCC model. Together, our study unveils a mechanism by which GOLM1 induces CD8+ T cells suppression through promoting PD-L1 stabilization and transporting PD-L1 into TAMs with exosome dependent. Targeting PD-L1+ TAM could be a novel strategy to enhance the efficacy of anti-PD-L1 therapy in HCC.

A nanounit strategy reverses immune suppression of exosomal PD-L1 and is associated with enhanced ferroptosis

In addition to increasing the expression of programmed death-ligand 1 (PD-L1), tumor cells can also secrete exosomal PD-L1 to suppress T cell activity. Emerging evidence has revealed that exosomal PD-L1 resists immune checkpoint blockade, and may contribute to resistance to therapy. In this scenario, suppressing the secretion of tumor-derived exosomes may aid therapy. Here, we develop an assembly of exosome inhibitor (GW4869) and ferroptosis inducer (Fe3+) via amphiphilic hyaluronic acid. Cooperation between the two active components in the constructed nanounit induces an anti-tumor immunoresponse to B16F10 melanoma cells and stimulates cytotoxic T lymphocytes and immunological memory. The nanounit enhances the response to PD-L1 checkpoint blockade and may represent a therapeutic strategy for enhancing the response to this therapy.

Nanoplasmonic Sandwich Immunoassay for Tumor-Derived Exosome Detection and Exosomal PD-L1 Profiling.

Tumor-derived exosomes play a vital role in the process of cancer development. Quantitative analysis of exosomes and exosome-shuttled proteins would be of immense value in understanding cancer progression and generating reliable predictive biomarkers for cancer diagnosis and treatment. Recent studies have indicated the critical role of exosomal programmed death ligand 1 (PD-L1) in immune checkpoint therapy and its application as a patient stratification biomarker in cancer immunotherapy. Here, we present a nanoplasmonic exosome immunoassay utilizing gold-silver (Au@Ag) core-shell nanobipyramids and gold nanorods, which form sandwich immune complexes with target exosomes. The immunoassay generates a distinct plasmonic signal pattern unique to exosomes with specific exosomal PD-L1 expression, allowing rapid, highly sensitive exosome detection and accurate identification of PD-L1 exosome subtypes in a single assay. The developed nanoplasmonic sandwich immunoassay provides a novel and viable approach for tumor cell-derived exosome detection and analysis with quantitative molecular details of key exosomal proteins, manifesting its great potential as a transformative diagnostic tool for early cancer detection, prognosis, and post-treatment monitoring.

CXCL10 Produced by HPV-Positive Cervical Cancer Cells Stimulates Exosomal PDL1 Expression by Fibroblasts via CXCR3 and JAK-STAT Pathways.

Persistent infection with human papillomavirus (HPV) and immune surveillance failure may be the initiating factors for the carcinogenesis of cervical squamous cell carcinoma (CSCC). HPV infection might affect the innate immune pathway of cervical epithelial cells that constitute the “microenvironment” for tumor cells. Programmed death-ligand 1 (PD-L1) has been reported to be an immunosuppressor that helps cancer cells escape the actions of T cells. In the present study, CXCL10 was substantially upregulated both in cervical tissues of HPV infected patients with cervical intraepithelial neoplasia (CIN) or CSCC, as well as in HPV16 E6/E7 transgenic murine cervix. The HPV-positive (HPV+) cervical cancer cell lines SiHa and Caski secreted increased levels of CXCL10 compared to human foreskin fibroblasts (HFF-1), and its receptor CXCR3 was overexpressed in HFF-1. After co-culture with SiHa or Caski, the JAK-STAT signaling pathway and exosomal PD-L1 expression were both upregulated in HFF-1. Recombinant human CXCL10 induced JAK-STAT and PD-L1, while the CXCL10-CXCR3 and JAK-STAT inhibitors AMG487 or ruxolitinib reduced the expression of PD-L1 in HFF-1 cells. Furthermore, the upregulated expression of PD-L1 was verified in HPV+ but not HPV-negative (HPV-) patients with cervical cancers by analysis of tissue microarray cores in 25 cervical lesion patients (P < 0.05). The results indicate that HPV infection can induce cervical cancer cells to secrete CXCL10, which binds to CXCR3 in the surrounding fibroblast cells,leading to JAK-STAT pathway activation and the subsequent upregulated expression of exosomal PD-L1. These mechanisms may help HPV to escape immune response attack, leading to carcinogenesis.

ExoHCR: a sensitive assay to profile PD-L1 level on tumor exosomes for immunotherapeutic prognosis

Cancer immunotherapy has made recent breakthrough, including immune checkpoint blockade (ICB) that inhibits immunosuppressive checkpoints such as programmed cell death protein 1 (PD-1) and programmed death-ligand 1 (PD-L1). However, most cancer patients do not durably respond to ICB. To predict ICB responses for patient stratification, conventional immunostaining has been used to analyze the PD-L1 expression level on biopsied tumor tissues but has limitations of invasiveness and tumor heterogeneity. Recently, PD-L1 levels on tumor cell exosomes showed the potential to predict ICB response. Here, we developed a non-invasive, sensitive, and fast assay, termed as exosome-hybridization chain reaction (ExoHCR), to analyze tumor cell exosomal PD-L1 levels. First, using αCD63-conjugated magnetic beads, we isolated exosomes from B16F10 melanoma and CT26 colorectal cancer cells that were immunostimulated to generate PD-L1-positive exosomes. Exosomes were then incubated with a conjugate of PD-L1 antibody with an HCR trigger DNA (T), in which one αPD-L1-T conjugate carried multiple copies of T. Next, a pair of metastable fluorophore-labeled hairpin DNA (H1 and H2) were added, allowing T on αPD-L1-T to initiate HCR in situ on bead-conjugated exosome surfaces. By flow cytometric analysis of the resulting beads, relative to αPD-L1-fluorophore conjugates, ExoHCR amplified the fluorescence signal intensities for exosome detection by 3–7 times in B16F10 cells and CT26 cells. Moreover, we validated the biostability of ExoHCR in culture medium supplemented with 50% FBS. These results suggest the potential of ExoHCR for non-invasive, sensitive, and fast PD-L1 exosomal profiling in patient stratification of cancer immunotherapy.

Exosomal PD-L1 and N-cadherin predict pulmonary metastasis progression for osteosarcoma patients

BackgroundRecent studies indicated that exosomal programmed death-ligand 1 (PD-L1) derived from cancers could induce immunosuppression and tumor pathogenesis. However, it is unclear how exosomes influence osteosarcoma (OS) progression and whether PD-L1 also exists in serum exosomes (Sr-exosomes) of patients with osteosarcoma. We examined serum exosomes from 70 OS patients, 9 patients with benign tumors and 22 healthy donors. OS-derived exosomes were functionally evaluated in vivo and in vitro.ResultsThe characteristics of exosomes derived from OS patient serum and OS cell lines were confirmed by several methods. We found OS patients had a higher level of exosomal PD-L1 compared to healthy donors. Meanwhile, OS patients with pulmonary metastasis also showed a relatively higher level of exosomal PD-L1 than patients without metastasis. Next, bioinformatic analysis demonstrated that Sr-exosomes isolated from OS patients may involve in the important process of immune function and cancer pathogenesis for OS patients. Co-expression network centered with PD-L1 among Sr-exosomal differently expressed mRNA demonstrated exosomal N-cadherin had a close relationship with exosomal PD-L1 expression. Then, we confirmed higher level of Sr-exosomal N-cadherin in OS patients with pulmonary metastasis compared to ones without metastasis. Furthermore, we elucidated osteosarcoma-derived exosomes and exosomal-PD-L1 promoted the pulmonary metastasis in metastatic models. ROC (Receiver Operating Characteristic Curve) analysis showed AUC (Area Under Curve) of 0.823 for exosomal PD-L1, 0.806 for exosomal N-cadherin and 0.817 for exosomal N-cadherin/E-cadherin to distinguish OS patients with pulmonary metastasis from ones without metastasis.ConclusionsOsteosarcoma stimulates pulmonary metastasis by releasing exosomes, that carry PD-L1 and N-cadherin. Detection of exosomal PD-L1 and N-cadherin from serum of OS patients may predict pulmonary metastasis progression for OS patients.

Transforming growth factor beta orchestrates PD-L1 enrichment in tumor-derived exosomes and mediates CD8 T-cell dysfunction regulating early phosphorylation of TCR signalome in breast cancer.

Tumor cells promote immune evasion through upregulation of programmed death-ligand 1 (PD-L1) that binds with programmed cell death protein 1 (PD1) on cytotoxic T cells and promote dysfunction. Though therapeutic efficacy of anti-PD1 antibody has remarkable effects on different type of cancers it is less effective in breast cancer (BC). Hence, more details understanding of PD-L1-mediated immune evasion is necessary. Here, we report BC cells secrete extracellular vesicles in form of exosomes carry PD-L1 and are highly immunosuppressive. Transforming growth factor beta (TGF-β) present in tumor microenvironment orchestrates BC cell secreted exosomal PD-L1 load. Circulating exosomal PD-L1 content is highly correlated with tumor TGF-β level. The later also found to be significantly associated with CD8+CD39+, CD8+PD1+ T-cell phenotype. Recombinant TGF-β1 dose dependently induces PD-L1 expression in Texos in vitro and blocking of TGF-β dimmed exosomal PD-L1 level. PD-L1 knocked down exosomes failed to suppress effector activity of activated CD8 T cells like tumor exosomes. While understanding its effect on T-cell receptor signaling, we found siPD-L1 exosomes failed to block phosphorylation of src family proteins, linker for activation of T cells and phosphoinositide phospholipase Cγ of CD8 T cells more than PD-L1 exosomes. In vivo inhibition of exosome release and TGF-β synergistically attenuates tumor burden by promoting Granzyme and interferon gamma release in tumor tissue depicting rejuvenation of exhausted T cells. Thus, we establish TGF-β as a promoter of exosomal PD-L1 and unveil a mechanism that tumor cells follow to promote CD8 T-cell dysfunction.

The Biogenesis, Biology, and Clinical Significance of Exosomal PD-L1 in Cancer.

The exosome serves as a trafficking vehicle for transport of programmed death-ligand 1 (PD-L1) into receptor cells. In tumor microenvironment, distant tumor cells can remotely attack activated T cells by exosomal PD-L1. Here, we summerize the biogenesis and transport process of exosomal PD-L1. Then, we focus on the cancer biology of exosomal PD-L1 in immunosuppression and the mechanism by which it inhibits T cells. Finally, we highlight the prospects of exosomal PD-L1 as a tumor biomarker and its significance in immunotherapy. In addition, we discuss the new challenges faced in researching and utilizing exosomal PD-L1. This review may shed light on the exosomal PD-L1 from the bench to the clinic. Exosomes serve as trafficking vehicles for transport of programmed death-ligand 1 (PD-L1) into receptor cells. In tumor microenvironment, distant tumor cells can remotely attack activated T cells through exosomal PD-L1. Here, we have summarized the biogenesis and transport of exosomal PD-L1. Next, we focused on the cancer biology of exosomal PD-L1 in immunosuppression and the mechanism by which it inhibits T cells. Finally, we highlighted the prospects of exosomal PD-L1 as a tumor biomarker and its significance in immunotherapy. In addition, we have discussed the new challenges faced in studying and utilizing exosomal PD-L1. This review may shed light on the translation of exosomal PD-L1 from bench to clinic.