PD-1/PD-L1 checkpoint blockade in immune-antitumortherapy:advances and perspectives

During the past three decades,studies have shown that tumor cells could"manipulate"host immunity to escape the immune defenses in the tumor microenvironment.One of the most important underlying mechanisms is immune-suppression regulated by programmed cell death-1 or its ligand 1(PD-1/PD-L1),which makes PD-1/PD-L1 blockadea promising target of cancer immune-therapy.Tumors could suppress immuno-response of T cells by activating PD-1/PD-L1 signaling pathway.Therefore,inhibiting the interaction between PD-1 and PD-L1 could reconstitute the enduring antitumor immunity in the tumor microenvironment via enhancing the T-cell response,there after augmenting the endogenous antitumor force of the immune system.Along these lines,inhibitors of PD-1/PD-L1 has been applied in multiple clinical trials against various types of tumors.Recent studies indicated that PD-1/PD-L1 blockade have demonstrated high efficacy and safety against melanoma,lung,kidney and several other solid tumors,as well as hematological malignancies.Nevertheless,the efficacy of this checkpoint blockade approach is not universal.Some investigation suggested that lack of responses to anti-PD-1/PD-L1 therapy of patients without PD-1/PD-L1 over-expression was expected.In this review,we summarize the history and current understanding of multiple intrinsic and extrinsic mechanisms via which PD-1/PD-L1 is regulated and research advances in preclinical/clinical aspects of PD-1/PD-L1,as well as significance and perspectives regarding the PD-1/PD-L1 blockade in immune-antitumor therapy.     

Th9 cells are subjected to PD-1/PD-L1-mediated inhibition and are capable of promoting CD8 T cell expansion through IL-9R in colorectal cancer

Th9 cells are named after their expression of IL-9. Studies in recent years demonstrated that Th9 cells could contribute to antitumor immunity by enhancing the recruitment and activation of mast cells, natural killer cells, CD8 T cells, and dendritic cells in the tumor microenvironment. To determine whether Th9 cells participate in colorectal cancer (CRC), we collected resected tumor samples from 20 CRC patients. In the tumor-infiltrating lymphocytes (TILs), IL-9⁺IL-4⁻ CD4⁺ T cells could be observed and were present at higher frequencies than the IL-9⁺IL-4⁺ and the IL-9⁻IL-4⁺ cells, suggesting that the majority of IL-9-producing TILs were bona fide Th9 cells. IL-9-secreting TILs presented particularly high PD-1 expression directly ex vivo. The expression of IL-9 was significantly reduced with PD-L1-mediated inhibition, which in turn was suppressed by anti-PD-1 blocking. Interestingly, the circulating CD4⁺ T cell compartment in CRC patients also presented Th9 enrichment, characterized by higher IL-9⁺IL-4⁻ and IL-9⁺IL-4⁺ cell frequencies in the CXCR3⁻CCR6⁻ compartment as compared to that in non-cancer controls. Using exogenous TGF-β and IL-4, we were capable of enriching Th9 cells without concurrent enrichment of Th2 cells. Th9-enriched CD4⁺ T cells, but not Th9-non-enriched cells, significantly increased the expansion of activated CD8⁺ T cells, in a manner that was dependent on the expression of IL-9R. In addition, the frequencies of Th9 cells in the tumor were positively correlated with the frequencies of CD8⁺ TILs. Together, we demonstrated that Th9 cells infiltrated CRC tumor, could be regulated via the PD-1/PD-L1 pathway, and could contribute the CD8⁺ T cell expansion.     

Remodeling “cold” tumor immune microenvironment via epigenetic-based therapy using targeted liposomes with in situ formed albumin corona

There is a close connection between epigenetic regulation, cancer metabolism, and immunology. The combination of epigenetic therapy and immunotherapy provides a promising avenue for cancer management. As an epigenetic regulator of histone acetylation, panobinostat can induce histone acetylation and inhibit tumor cell proliferation, as well as regulate aerobic glycolysis and reprogram intratumoral immune cells. JQ1 is a BRD4 inhibitor that can suppress PD-L1 expression. Herein, we proposed a chemo-free, epigenetic-based combination therapy of panobinostat/JQ1 for metastatic colorectal cancer. A novel targeted binary-drug liposome was developed based on lactoferrin-mediated binding with the LRP-1 receptor. It was found that the tumor-targeted delivery was further enhanced by in situ formation of albumin corona. The lactoferrin modification and endogenous albumin adsorption contribute a dual-targeting effect on the receptors of both LRP-1 and SPARC that were overexpressed in tumor cells and immune cells (e.g., tumor-associated macrophages). The targeted liposomal therapy was effective to suppress the crosstalk between tumor metabolism and immune evasion via glycolysis inhibition and immune normalization. Consequently, lactic acid production was reduced and angiogenesis inhibited; TAM switched to an anti-tumor phenotype, and the anti-tumor function of the effector CD8⁺ T cells was reinforced. The strategy provides a potential method for remodeling the tumor immune microenvironment (TIME).     

Breast cancer cells promote CD169+ macrophage-associated immunosuppression through JAK2-mediated PD-L1 upregulation on macrophages

Macrophages are recognized as one of the major cell types in tumor microenvironment, and macrophage infiltration has been predominantly associated with poor prognosis among patients with breast cancer. Using the murine models of triple-negative breast cancer in CD169-DTR mice, we found that CD169⁺ macrophages support tumor growth and metastasis. CD169⁺ macrophage depletion resulted in increased accumulation of CD8⁺ T cells within tumor, and produced significant expansion of CD8⁺ T cells in circulation and spleen. In addition, we observed that CD169⁺ macrophage depletion alleviated tumor-induced splenomegaly in mice, but had no improvement in bone loss and repression of bone marrow erythropoiesis in tumor-bearing mice. Cancer cells and tumor associated macrophages exploit the upregulation of the immunosuppressive protein PD-L1 to subvert T cell-mediated immune surveillance. Within the tumor microenvironment, our understanding of the regulation of PD-L1 protein expression is limited. We showed that there was a 5-fold higher relative expression of PD-L1 on macrophages as compared with 4T1 tumor cells; coculture of macrophages with 4T1 cells augmented PD-L1 levels on macrophages, but did not upregulate the expression of PD-L1 on 4T1 cells. JAK2/STAT3 signaling pathway was activated in macrophages after coculture, and we further identified the JAK2 as a critical regulator of PD-L1 expression in macrophages during coculture with 4T1 cells. Collectively, our data reveal that breast cancer cells and CD169⁺ macrophages exhibit bidirectional interactions that play a critical role in tumor progression, and inhibition of JAK2 signaling pathway in CD169⁺ macrophages may be potential strategy to block tumor microenvironment-derived immune escape.     

Cancer-cell-biomimetic nanoparticles systemically eliminate hypoxia tumors by synergistic chemotherapy and checkpoint blockade immunotherapy

Checkpoint blockade-based immunotherapy has shown unprecedented effect in cancer treatments, but its clinical implementation has been restricted by the low host antitumor response rate. Recently, chemotherapy is well recognized to activate the immune system during some chemotherapeutics-mediated tumor eradication. The enhancement of immune response during chemotherapy might further improve the therapeutic efficiency through the synergetic mechanism. Herein, a synergistic antitumor platform (designated as BMS/RA@CC-Liposome) was constructed by utilizing CT26 cancer-cell-biomimetic nanoparticles that combined chemotherapeutic drug (RA-V) and PD-1/PD-L1 blockade inhibitor (BMS-202) to remarkably enhance antitumor immunity. In this study, the cyclopeptide RA-V as chemotherapeutic drugs directly killing tumor cells and BMS-202 as anti-PD agents eliciting antitumor immune responses were co-encapsulated in a pH-sensitive nanosystem. To achieve the cell-specific targeting drug delivery, the combination therapy nanosystem was functionalized with cancer cell membrane camouflage. The biomimetic drug delivery system perfectly disguised as endogenous substances, and realized elongated blood circulation due to anti-phagocytosis capability. Moreover, the BMS/RA@CC-Liposome also achieved the selective targeting of CT26 cells by taking advantage of the inherent homologous adhesion property of tumor cells. The in vitro and in vivo experiments revealed that the BMS/RA@CC-Liposome realized PD-1/PD-L1 blockade-induced immune response, RA-V-induced PD-L1 down-regulation and apoptosis in cancer cells. Such a system combining the advantages of chemotherapy and checkpoint blockade-based immunotherapy to create an immunogenic tumor microenvironment systemically, demonstrated improved therapeutic efficacy against hypoxic tumor cells and offers an alternative strategy based on the immunology of the PD-1/PD-L1 pathway.     

Cdk5 knocking out mediated by CRISPR-Cas9 genome editing for PD-L1 attenuation and enhanced antitumor immunity

Blocking the programmed death-ligand 1 (PD-L1) on tumor cells with monoclonal antibody therapy has emerged as powerful weapon in cancer immunotherapy. However, only a minority of patients presented immune responses in clinical trials. To develop an alternative treatment method based on immune checkpoint blockade, we designed a novel and efficient CRISPR-Cas9 genome editing system delivered by cationic copolymer aPBAE to downregulate PD-L1 expression on tumor cells via specifically knocking out Cyclin-dependent kinase 5 (Cdk5) gene in vivo. The expression of PD-L1 on tumor cells was significantly attenuated by knocking out Cdk5, leading to effective tumor growth inhibition in murine melanoma and lung metastasis suppression in triple-negative breast cancer. Importantly, we demonstrated that aPBAE/Cas9-Cdk5 treatment elicited strong T cell-mediated immune responses in tumor microenvironment that the population of CD8⁺ T cells was significantly increased while regulatory T cells (Tregs) was decreased. It may be the first case to exhibit direct in vivo PD-L1 downregulation via CRISPR-Cas9 genome editing technology for cancer therapy. It will provide promising strategy for preclinical antitumor treatment through the combination of nanotechnology and genome engineering.     

Blocking PD-1/PD-L1 by an ADCC enhanced anti-B7-H3/PD-1 fusion protein engages immune activation and cytotoxicity

Antibody therapy based on PD-1/PD-L1 blocking or ADCC effector has produced significant clinical benefit for cancer patients. We generated a novel anti-B7-H3 antibody (07B) and engineered the Fc fragment to enhance ADCC. To improve efficacy and tumor selectivity, we developed anti-B7-H3/PD-1 bispecific fusion proteins that simultaneously engaged tumor associate marker B7-H3 and immune suppressing ligand PD-L1 as well as enhanced ADCC to promote potent and highly selective tumor killing. Fusion proteins were designed by fusing human PD-1 extra domain to 07B in four different formats and showed good binding capacity to both targets. Indeed, the affinity of fusion proteins to B7-H3 is over 10,000 fold higher compared to that of the analogous PD-L1 and the blocking of fusion proteins to PD-L1 was worse but it greatly enhanced when bound to B7-H3, thus achieving directly PD-L1-blockade to B7-H3-expressing tumor cells. Importantly, IL-2 production was enhanced by fusion proteins from staphylococcal enterotoxin B (SEB) stimulated PBMC. Similarly, cytokines induced by fusion proteins was enhanced when co-cultured with stimulated CD8⁺ T cells and B7-H3/PD-L1 transfected raji cells. Additionally, fusion proteins improved activation to CD16a by Fc modification and delivered selective cytotoxicity to B7-H3 expressing tumor cells. In conclusion, fusion proteins blocked the PD-1/PD-L1 signal pathway and significantly increased potency of ADCC in a B7-H3-directed manner, thereby selectively activating CD8⁺ T cells and enhancing natural killing towards tumor. This novel fusion protein with its unique targeting preference may be useful to enhance efficacy and safety of immunotherapy for B7-H3-overexpressing malignancies.     

CD30L/CD30 signaling regulates the formation of the tumor immune microenvironment and inhibits intestinal tumor development of colitis-associated colon cancer in mice

Inflammatory bowel disease is one of the major causes of colitis-associated colon cancer (CAC). Therefore, it is necessary to explore new therapies to prevent colon cancer (CRC) in view of the relationship between chronic inflammation and tumor development. Previous studies on the correlation between CD30L/CD30 and cancer were mostly limited to lymphoid or homogenous tumors, while there have been only a few reports on the role of CD30L/CD30 signal transduction in the pathogenesis of CAC. In this study, we established an AOM/DSS-induced CAC model with CD30LKO mice to explore the effect of CD30L/CD30 signal transduction on the formation of the intestinal tumor immune microenvironment (TIME) during the development of intestinal tumors. Our results revealed that CD30L deficiency promoted the accumulation of myeloid derived suppressor cells (MDSCs), increased the expression of PD-L1 on MDSCs and tumor associated macrophages (TAMs), and enhanced the secretion of various inflammatory and immunosuppressive factors in the intestinal mucosa of CAC mice. Furthermore, CD30L gene deletion could selectively promote the upregulation of PD-1 expression on CD4⁺ and CD8⁺ T cells and inhibit their activation, differentiation and secretion of effector cytokines, which led to an attenuation of antitumor immune responses mediated by T_EM (CD44⁺CD62L^-) cells. Thus, our data suggest that CD30L/CD30 signaling might be a potential candidate target for immunological therapy in CAC.     

PD-1 blockade augments humoral immunity through ICOS-mediated CD4+ T cell instruction

Successful applications of PD-1/PD-L1 blockade in multiple cancers highlight the efficacy of immunotherapy mediated by enhancing CD8⁺ T cell immunity both in mouse and human. How PD-1 blockade affects humoral immunity remains unclear. Herein we demonstrated that treatment of anti-PD-1 antibody led to the increase in both total IgG and OVA-specific IgG in OVA-immunized mice. However, no effect was observed on Ab affinity maturation. Accumulation of germinal center (GC) and memory B cells was observed in the spleens together with elevated percentages of plasma cells in the spleens and bone marrow. More interestingly, dramatic infiltration of CD4⁺ T cells was apparent in GCs after PD-1 blockade with a significant increase in the expression of ICOS. When CD4⁺ T cells and B cells from OVA-immunized mice were co-cultured with neutralizing anti-PD-1 Ab in vitro, PD-1 blockade recapitulated the up-regulation of ICOS expression on CD4⁺ T cells with the activation of ERK signaling. Suppression of ERK activation not only reduced ICOS expression on CD4⁺ T cells but also attenuated IgG production upon PD-1 blockade. Taken together, PD-1 blockade enhances humoral immunity. This process partially relies on more accumulation of CD4⁺ T cells in GCs with the up-regulation of ICOS expression and the promotion of B cell terminal differentiation. The regulatory pattern of PD-1 blockade illustrated here provides a new mechanism of how immune checkpoint molecules regulating humoral immune responses.     

Tubeimoside-1 induces TFEB-dependent lysosomal degradation of PD-L1 and promotes antitumor immunity by targeting mTOR

Programmed cell death ligand 1 (PD-L1)/programmed cell death protein 1 (PD-1) cascade is an effective therapeutic target for immune checkpoint blockade (ICB) therapy. Targeting PD-L1/PD-1 axis by small-molecule drug is an attractive approach to enhance antitumor immunity. Using flow cytometry-based assay, we identify tubeimoside-1 (TBM-1) as a promising antitumor immune modulator that negatively regulates PD-L1 level. TBM-1 disrupts PD-1/PD-L1 interaction and enhances the cytotoxicity of T cells toward cancer cells through decreasing the abundance of PD-L1. Furthermore, TBM-1 exerts its antitumor effect in mice bearing Lewis lung carcinoma (LLC) and B16 melanoma tumor xenograft via activating tumor-infiltrating T-cell immunity. Mechanistically, TBM-1 triggers PD-L1 lysosomal degradation in a TFEB-dependent, autophagy-independent pathway. TBM-1 selectively binds to the mammalian target of rapamycin (mTOR) kinase and suppresses the activation of mTORC1, leading to the nuclear translocation of TFEB and lysosome biogenesis. Moreover, the combination of TBM-1 and anti-CTLA-4 effectively enhances antitumor T-cell immunity and reduces immunosuppressive infiltration of myeloid-derived suppressor cells (MDSCs) and regulatory T (Treg) cells. Our findings reveal a previously unrecognized antitumor mechanism of TBM-1 and represent an alternative ICB therapeutic strategy to enhance the efficacy of cancer immunotherapy.     

Abrogation of HnRNP L enhances anti-PD-1 therapy efficacy via diminishing PD-L1 and promoting CD8+ T cell-mediated ferroptosis in castration-resistant prostate cancer

Owing to incurable castration-resistant prostate cancer (CRPC) ultimately developing after treating with androgen deprivation therapy (ADT), it is vital to devise new therapeutic strategies to treat CRPC. Treatments that target programmed cell death protein 1 (PD-1) and programmed death ligand-1 (PD-L1) have been approved for human cancers with clinical benefit. However, many patients, especially prostate cancer, fail to respond to anti-PD-1/PD-L1 treatment, so it is an urgent need to seek a support strategy for improving the traditional PD-1/PD-L1 targeting immunotherapy. In the present study, analyzing the data from our prostate cancer tissue microarray, we found that PD-L1 expression was positively correlated with the expression of heterogeneous nuclear ribonucleoprotein L (HnRNP L). Hence, we further investigated the potential role of HnRNP L on the PD-L1 expression, the sensitivity of cancer cells to T-cell killing and the synergistic effect with anti-PD-1 therapy in CRPC. Indeed, HnRNP L knockdown effectively decreased PD-L1 expression and recovered the sensitivity of cancer cells to T-cell killing in vitro and in vivo, on the contrary, HnRNP L overexpression led to the opposite effect in CRPC cells. In addition, consistent with the previous study, we revealed that ferroptosis played a critical role in T-cell-induced cancer cell death, and HnRNP L promoted the cancer immune escape partly through targeting YY1/PD-L1 axis and inhibiting ferroptosis in CRPC cells. Furthermore, HnRNP L knockdown enhanced antitumor immunity by recruiting infiltrating CD8⁺ T cells and synergized with anti-PD-1 therapy in CRPC tumors. This study provided biological evidence that HnRNP L knockdown might be a novel therapeutic agent in PD-L1/PD-1 blockade strategy that enhanced anti-tumor immune response in CRPC.     

Gemcitabine and checkpoint blockade exhibit synergistic anti-tumor effects in a model of murine lung carcinoma

Lung cancer is leading cause of cancer death in the world. Chemotherapy is currently one of the standard treatments for lung cancer. Gemcitabine is a pyrimidine nucleoside drug which has been approved by FDA to treat lung cancer. However, acquired resistance inevitable develops after Gemcitabine treatment, limiting clinical efficacy. Lewis lung carcinoma (LLC) cells were treated with Gemcitabine and cell apoptosis and programmed cell death-ligand 1 (PD-L1) expression were analyzed by flow cytometry. LLC mouse model was established to analysis the proportion and programmed cell death-1 (PD-1) expression of CD8 + T cells. Anti-tumor effect by treating with Gemcitabine and anti-PD-1 antibody was measured through in vivo LLC mouse model. Gemcitabine treatment induces tumor cell apoptosis and PD-L1 expression. Further study showed that Gemcitabine treatment also increases CD8⁺ and CD4⁺ T cells proportion, PD-1 and PD-L1 expression in LLC mouse model. Combination therapy with Gemcitabine and αPD-1 not only has strong anti-tumor effect, but also could inhibit postsurgical recurrence of LLC. Our findings demonstrated that the combination therapy of Gemcitabine and αPD-1 is an effective therapeutic strategy for lung cancer.     

Novel phthalimides regulating PD-1/PD-L1 interaction as potential immunotherapy agents

Programmed cell death 1(PD-1)/programmed cell death ligand 1(PD-L1) have emerged as one of the most promising immune checkpoint targets for cancer immunotherapy. Despite the inherent advantages of small-molecule inhibitors over antibodies, the discovery of small-molecule inhibitors has fallen behind that of antibody drugs. Based on docking studies between small molecule inhibitor and PD-L1 protein, changing the chemical linker of inhibitor from a flexible chain to an aromatic ring may improve its binding capacity to PD-L1 protein, which was not reported before. A series of novel phthalimide derivatives from structure-based rational design was synthesized. P39 was identified as the best inhibitor with promising activity, which not only inhibited PD-1/PD-L1 interaction (IC₅₀ = 8.9 nmol/L), but also enhanced killing efficacy of immune cells on cancer cells. Co-crystal data demonstrated that P39 induced the dimerization of PD-L1 proteins, thereby blocking the binding of PD-1/PD-L1. Moreover, P39 exhibited a favorable safety profile with a LD₅₀ > 5000 mg/kg and showed significant in vivo antitumor activity through promoting CD8⁺ T cell activation. All these data suggest that P39 acts as a promising small chemical inhibitor against the PD-1/PD-L1 axis and has the potential to improve the immunotherapy efficacy of T-cells.     

PD-1 regulates CXCR5+ CD4 T cell-mediated proinflammatory functions in non-small cell lung cancer patients

PD-1 inhibitors have been used to revive exhausted T cell responses in non-small cell lung cancer (NSCLC) and other malignancies. CXCR5⁺ T follicular helper (Tfh) cells are characterized by constitutive high PD-1 expression and have been associated with the formation of tertiary lymphoid structures and implicated in antitumor immunity. In this study, we investigated the effect of PD-1 and PD-1 inhibition on CXCR5⁺ CD4 T cells. Data showed that CXCR5⁺ CD4 T cells in both healthy subjects and NSCLC patients presented markedly higher PD-1 expression than CXCR5⁻ CD4 T cells. Both CXCR5⁻ and CXCR5⁺ CD4 T cells from NSCLC patients presented higher PD-1 expression than their counterparts in healthy subjects. PD-1⁺ CXCR5⁺ CD4 T cells were functional, could express IL-21, IL-10, and CXCL13 upon stimulation, demonstrated auxiliary effects toward CD8 T cell-mediated IFN-γ production and proliferation, and promoted IgM and IgG production. However, the potency of PD-1⁺ CXCR5⁺ CD4 T cells was lower than the potency of PD-1⁻ CXCR5⁺ CD4 T cells. PD-1 blocking could significantly enhance the effector functions of PD-1⁺ CXCR5⁺ CD4 T cells. Overall, this study demonstrated that PD-1⁺ CXCR5⁺ CD4 T cells could promote CD8 T cell and B cell inflammation and could be modulated by PD-1 inhibition.     

Role of CD8+ T lymphocyte cells: Interplay with stromal cells in tumor microenvironment

CD8⁺ T lymphocytes are pivotal cells in the host response to antitumor immunity. Tumor-driven microenvironments provide the conditions necessary for regulating infiltrating CD8⁺ T cells in favor of tumor survival, including weakening CD8⁺ T cell activation, driving tumor cells to impair immune attack, and recruiting other cells to reprogram the immune milieu. Also in tumor microenvironment, stromal cells exert immunosuppressive skills to avoid CD8⁺ T cell cytotoxicity. In this review, we explore the universal function and fate decision of infiltrated CD8⁺ T cells and highlight their antitumor response within various stromal architectures in the process of confronting neoantigen-specific tumor cells. Thus, this review provides a foundation for the development of antitumor therapy based on CD8⁺ T lymphocyte manipulation.KEY WORDS: CD8⁺ T lymphocyte, Stromal cell, Tumor microenvironment, Immunosuppression, Immunotherapy, Antitumor     

Macrophage-mediated tumor-targeted delivery of engineered Salmonella typhimurium VNP20009 in anti-PD1 therapy against melanoma

Bacterial antitumor therapy has great application potential given its unique characteristics, including genetic manipulation, tumor targeting specificity and immune system modulation. However, the nonnegligible side effects and limited efficacy of clinical treatment limit their biomedical applications. Engineered bacteria for therapeutic applications ideally need to avoid their accumulation in normal organs and possess potent antitumor activity. Here, we show that macrophage-mediated tumor-targeted delivery of Salmonella typhimurium VNP20009 can effectively reduce the toxicity caused by administrating VNP20009 alone in a melanoma mouse model. This benefits from tumor-induced chemotaxis for macrophages combined with their slow release of loaded strains. Inspired by changes in the tumor microenvironment, including a decrease in intratumoral dysfunctional CD8⁺ T cells and an increase in PDL1 on the tumor cell surface, macrophages were loaded with the engineered strain VNP-PD1nb, which can express and secrete anti-PD1 nanoantibodies after they are released from macrophages. This novel triple-combined immunotherapy significantly inhibited melanoma tumors by reactivating the tumor microenvironment by increasing immune cell infiltration, inhibiting tumor cell proliferation, remodeling TAMs to an M1-like phenotype and prominently activating CD8⁺ T cells. These data suggest that novel combination immunotherapy is expected to be a breakthrough relative to single immunotherapy.     

Function of follicular helper T cell is impaired and correlates with survival time in non-small cell lung cancer

Non-small cell lung cancer (NSCLC) represents one of the most common and aggressive cancers worldwide. The PD-1/PD-L1 interaction plays important roles in cancer immunology, and expression of PD-L1 has been discovered in NSCLC tumor cells. Since follicular helper T (Tfh) cells have characteristic high PD-1 expression, we therefore investigated the inflammatory status of Tfh in NSCLC. CD4⁺ CXCR5⁺ T cell population was examined to define Tfh cells. Data showed that frequency of Tfh cells in peripheral blood was significantly lower in NSCLC patients than in healthy controls. In both primary and metastatic tumors, infiltration of Tfh cells was observed, suggesting that they participated in the antitumor immunity of NSCLC patients. Compared to other T cell subsets, the Tfh cells from the peripheral blood and the resected tumors of NSCLC patients presented elevated apoptosis and reduced proliferation capacity. The Tfh cells from NSCLC patients were also less effective at downregulating IgD and upregulating CD27 expression in naive B cells, and induced less IgM, IgG and IgA secretion, than those from healthy controls. We then found that the survival time from the date of surgery was positively correlated with the frequency of tumor-infiltrating Tfh cells in NSCLC subjects. Overall, the results from this study demonstrated that the Tfh cells were likely involved in the antitumor immunity and were associated with better clinical outcomes, but suffered strong immunosuppression in NSCLC. Enhancing the Tfh cell activity therefore represents a potential therapeutic strategy in NSCLC.     

基于生物信息学的CD39对肺腺癌免疫微环境及其免疫治疗的影响分析

目的 采用生物信息学方法探讨CD39基因在肺腺癌组织中的表达情况,并分析CD39与肺腺癌免疫微环境及免疫治疗响应的关系。方法 通过The Cancer Genome Atlas （TCGA）数据库分析CD39在肺腺癌组织和正常肺组织中的表达差异。采用基因集富集分析（GSEA）研究CD39可能富集的免疫相关通路;通过肿瘤免疫数据库（TIMER）分析肺腺癌患者中CD39基因表达情况与肿瘤微环境免疫细胞浸润的关系;同时分析CD39和其他免疫检查点基因PD-1、PD-L1、CTLA-4、IDO1的相关性,采用药物敏感性基因组学数据库（GDSC）和肿瘤免疫功能障碍和排斥（TIDE）数据库,预测CD39基因表达与化疗药物敏感性以及免疫治疗的响应。结果 CD39在肺腺癌组织中的表达低于在正常组织中的表达,CD39富集了免疫相关通路如炎症反应、干扰素α反应、干扰素γ反应。TIMER数据库均显示在肺腺癌组织中,CD39的表达与B细胞、CD8⁺T细胞、CD4⁺T细胞、巨噬细胞、中性粒细胞以及树突状细胞呈正相关性。同时CD39与其他的免疫检查点PD-1、PD-L1、CTLA-4、IDO1均呈一定的正相关性,化疗敏感性显示在肺腺癌组织中,对于博来霉素、顺铂、多西他赛、长春花碱等化疗药物,高表达CD39组对其敏感。但对于免疫治疗,其响应率却低于CD39低表达组。结论 CD39在肺腺癌组织中低表达,能激活免疫相关通路,对免疫治疗响应率高,可作为肺腺癌新型分子标志物。     

The PD-1/PD-L1 pathway: biological background and clinical relevance of an emerging treatment target in immunotherapy

Introduction: The co-inhibitory receptor programmed death 1 (PD-1) and its ligands are key regulators in a wide spectrum of immune responses and play a critical role in autoimmunity and self-tolerance as well as in cancer immunology. Emerging evidence suggests that cancer cells might use the PD-1/PD-ligand (PD-L) pathway to escape anti-tumor immunity. Based on this evidence, early phase human clinical trials targeting the PD-1/PD-L pathway are currently underway for multiple human cancers.

Areas covered: The role of the PD-1/PD-L pathway in autoimmune disease, viral infections as well as in malignant neoplasms is discussed and an overview of the existing therapeutics as well as the results of clinical trials targeting this pathway in cancer is given.

Expert opinion: The PD-1/PD-L pathway represents an important mechanism of immune evasion for malignant neoplasms. Early clinical trials indicate effectiveness of PD-1/PD-L pathway blockade in several solid cancers. However, greater insight into the exact mechanisms by which tumors are able to evade anti-tumor immunity is needed to increase clinical effectiveness, for example by combination blockade of diverse co-inhibitory receptors.