PD-1单抗和PD-L1单抗同是免疫药物，却有四大不同

<正>随着首款PD-L1单抗正式上市中国,国内目前免疫药物主要有PD-1单抗和PD-L1单抗两大类。PD-1-PD-L1通路是抑制免疫反应的信号通路。肿瘤细胞表达PD-L1,与淋巴细胞表面PD-1结合,从而抑制淋巴细胞对肿瘤杀伤,实现"免疫逃逸"。PD-1/PD-L1单抗是分别作用于肿瘤细胞上PD-L1或淋巴细胞上PD-1位点,阻止两者相互结合,激活免疫细胞杀伤肿瘤。     

PD-L1分子在肺癌细胞株上的表达及其生物学意义

背景与目的目前研究表明,多种人类肿瘤大量表达的PD-L1分子参与了肿瘤免疫逃逸,其机制主要在于肿瘤细胞通过高表达PD-L1分子,与T细胞上的受体PD-1的结合,传递负性调控信号,导致肿瘤抗原特异性T细胞的凋亡和免疫无能。本文着重探讨PD-L1分子在肺癌细胞株上的表达及其对T细胞杀伤效应的调节作用。方法采用常规方法从健康人外周血单个核细胞诱导DCs,并经凋亡肿瘤细胞和激发型CD40单克隆抗体刺激获得成熟DCs,与自体T细胞共育后获得肿瘤特异性CTL细胞;流式细胞术检测肺癌细胞上PD-L1分子的表达;JAM法和单抗阻断实验分析CTL细胞对肺癌细胞株的杀伤效应,ELISA法检测细胞培养上清中IFN-γ的含量。结果经凋亡肿瘤细胞负载的成熟DCs可诱导自体T细胞分化为肿瘤特异性CTL;H1299高表达PD-L1分子(90.3±4.2)%,而A549低表达PD-L1分子(19.4±5.2)%;CTL对A549具有高效特异的杀伤力,而对H1299不能高效杀伤;联合应用PD-L1单抗可促进CTL对H1299的杀伤作用和IFN-γ的分泌(P<0.05)。结论在肺癌细胞株上表达的PD-L1分子,可降低CTL对肺癌细胞的杀伤效应。     

树突状细胞对肿瘤浸润淋巴细胞抗小鼠肝癌活性影响的研究

目的探讨H22细胞全细胞性抗原致敏的DC激活的TIL体外抗小鼠肝癌活性,并将H22-DC-TIL过继免疫荷瘤小鼠,研究其对荷瘤小鼠免疫功能的影响及抑瘤作用。方法从小鼠四肢长骨骨髓中获取DC,应用粒/巨噬细胞集落刺激因子(GM-CSF)、白介素-4(IL-4)和肿瘤全细胞性抗原致敏DC,然后用DC激活TIL,观察TIL在体外对H22细胞、Hepal-6细胞和B16细胞的杀伤活性;检测应用H22-DC-TIL后荷瘤小鼠的脾淋巴细胞的NK、LAK、CTL活性、血清TNF活性、抑瘤作用以及瘤体病理改变,并与对照组相比较。结果①H22-DC-TIL具有很强的对H22细胞杀伤活性[杀伤率为(71.31±3.11)%],明显高于其对Hepal-6和B16细胞的杀伤活性[杀伤率分别为(50.11±3.03)%,(30.31±2.89)%],也明显高于未经DC激活的TIL、H22-DC-脾淋巴细胞和未经DC激活的脾淋巴细胞对H22细胞杀伤活性[杀伤率分别为(49.80±3.21)%,(48.76±3.60)%和(19.23±2.71)%]和对Hepal-6细胞杀伤活性[杀伤率分别为(39.40±3.21)%,(38.62±2.87)%和(18.73±2.40)%]以及对B16细胞杀伤活性[杀伤率分别为(26.38±2.51)%,(25.82±2.70)%和(18.34±3.01)%],同时B16-DC-TIL(TIL来源于H22瘤体)也可诱导相对较低的对B16细胞的特异性细胞杀伤活性。②H22-DC-TIL可明显诱导提高荷瘤脾淋巴细胞NK、LAK和CTL活性[活性为(30.43±1.35)%、(31.40±1.80)%、(35.30±1.20)%],并可检测到血清TNF水平明显上升[血清TNF为(40.41±1.85)U/ml],它们均达正常对照组水平,与未经DC激活的TIL组、H22-DC-脾淋巴细胞组、未经DC激活的脾淋巴细胞组、生理盐水组分别对应比较,差异均有显著性(P<0.01)。该组瘤体内淋巴细胞浸润程度也高于对照组,其瘤体生长明显受到抑制。结论①H22-DC-TIL可产生很强的体外针对H22细胞的特异性杀伤活性。②H22-DC-TIL具有很强的特异性抗小鼠肝癌作用。     

丹参水溶性组分SABP对小鼠肝癌免疫微环境的影响

目的 探讨丹参水溶性组分SABP影响H22细胞肝癌原位移植瘤生长及肝癌免疫微环境的效应。方法 建立H22细胞肝癌原位移植瘤小鼠模型。ELISA检测肝脏中PD-L1、TGF-β、IL-1β、IL-10、IL-4、IFN-γ、IL-18、IL-7、IL-2、CCL-2和CCL-21的表达量。计算肝脏、脾脏和肾脏的脏器系数。结果 SABP抑制H22细胞肝癌原位移植瘤的生长,提高肝癌微环境中PD-L1、TGF-β、IL-1β和IL-10的表达水平,增加了肝、脾和肾系数。结论 SABP能抑制H22细胞肝癌原位移植瘤生长,促进肝癌微环境中PD-L1、TGF-β、IL-1β和IL-10抑制性免疫分子的表达。     

抑制乳腺癌患者自体CD3AK细胞PD-1的表达对杀伤MCF-7/adr细胞的影响北大核心CSCD

目的探讨抑制PD-1表达后的乳腺癌患者自体CD3AK细胞对乳腺癌MCF-7/adr细胞的杀伤作用。方法采用慢病毒介导反转录技术将已构建的PD-1重组质粒转染入CD3AK细胞抑制PD-1的表达,流式细胞法检测PD-L1的表达情况;CD3AK细胞与MCF-7/adr细胞共培养,CCK-8法测定各组的杀伤率,分别由荷瘤BALB/c裸鼠尾静脉注入空白质粒组和PD-1质粒组细胞和0.9%氯化钠溶液,观察各组的抑瘤作用。结果反转录技术可有效抑制CD3AK细胞PD-1的表达(P<0.01);RT-PCR结果显示lentiviral vector/PD-1使CD3AK细胞PD-1基因表达水平降低;CCK-8结果显示培养第14、21天的空白质粒组和PD-1质粒组对MCF-7/adr细胞的杀伤率分别为42.98%和62.68%,47.22%和66.95%(P<0.01);裸鼠体内实验表明,PD-1质粒组CD3AK细胞能够显著抑制肿瘤的生长,其抑瘤率可达74.8%。结论 MCF-7/adr细胞表面高表达PD-L1,抑制PD1的表达可有效提高CD3AK细胞的杀伤能力。     

PD-1/PD-L1 抑制剂在肿瘤免疫治疗中的研究进展*

肿瘤免疫治疗是目前肿瘤领域的研究热点,是一种疗效显著的肿瘤治疗模式。程序性死亡受体PD- 1（programmed cell death-1）是一种重要的免疫抑制分子,主要在激活的T 细胞和B 细胞中表达。肿瘤细胞中高表达PD- 1 的配体PD-L1,导致肿瘤微环境中PD- 1 通路持续激活。PD- 1/PD-L 1 抑制剂可以阻断PD- 1 与PD-L1 的结合,阻断负向调控信号,使T 细胞恢复活性,从而增强免疫应答。近期研究发现PD- 1 和PD-L1 的抑制剂在多种肿瘤类型中疗效显著。本文对PD- 1/PD-L 1 抑制剂的现况及其对不同肿瘤类型临床疗效的研究进展进行综述。      

HIFU治疗后肿瘤抗原对树突状细胞的活化及其抗肿瘤效应

目的：探讨HIFU治疗小鼠H22抑制性肝癌后产生的肿瘤抗原对机体抗肿瘤免疫功能增强的机制。方法：正常小鼠骨髓中提取骨髓细胞,在rmIL-4、rmGM-CSF奈件下培养7d,制备小鼠骨髓树突状细胞,用HIFU治疗小鼠移植性肝癌后产生的肿瘤抗原活化树突状细胞,再用活化后的树突状细胞激活T淋巴细胞为细胞毒性T细胞,用MTT法检测CTL在体外特异性杀伤肿瘤靶细胞的能力。结果：B16肿瘤HSP70-肽复合物组和H22肿瘤HSP70-肽复合物组的脾淋巴细胞的增殖率均高于阴性对照组、H22肿瘤粗提物组和HIFU后H22肿瘤粗提物组,P〈0．001;但两组之间差异无统计学意义,P〉0．05。H22肿瘤HSP70-肽复合物组CTL对H22肿瘤细胞的杀伤率为70．0％,明显高于阴性对照组、H22肿瘤粗提物组和HIFU后H22肿瘤粗提物组（P〈0．001）,但对非靶细胞B16肿瘤的杀伤率与上述各组的差异无统计学意义;B16肿瘤HSP70-肽复合物组CTL对B16肿瘤细胞的杀伤率为78．5％,对H22细胞的杀伤率为21．4％,表明CTL对肿瘤细胞的杀伤作用具有特异性。结论：HIFU治疗后坏死肿瘤组织中的HSP70-肽复合物作为肿瘤疫苗,通过活化DC和刺激T淋巴细胞增殖为CTL,发挥特异性抗肿瘤免疫功能。     

小鼠H-2K b基因转染人肝癌细胞后激活免疫排斥反应的研究

目的：增强人肝癌细胞的免疫原性以激活宿主免疫细胞识别杀伤相应的肝癌细胞。方法：以脂质体介导小鼠Ｈ－２Ｋｂ基因转染肝癌细胞株,并检测Ｈ－２Ｋｂ抗原表达情况,然后用Ｈ－２Ｋｂ基因转染后的肝癌细胞体外激活效应细胞杀伤活性,再进行裸鼠动物实验。结果：Ｈ－２Ｋｂ基因转染人肝癌细胞株ＨｅｐＧ２后,Ｓｏｕｔｈｅｍ印迹杂交结果显示,Ｈ－２Ｋｂ基因整合于肿瘤细胞染色体中,ＲＮＡ点杂交结果显示,Ｈ－２ＫｂＤＮＡ已转录成ｍＲＮＡ。免疫组化及流式细胞仪检测显示,Ｈ－２Ｋｂ抗原已在肝癌细胞胞膜上表达。转染后肝癌细胞在体外能强烈诱发效应细胞毒性,这种细胞毒性现象在裸鼠实验中得到进一步验证。结论：异源ＭＨＧ－Ｉ类基因Ｈ－２Ｋｂ转染肝癌细胞后可增强其免疫原性并激活免疫效应细胞杀伤活性。     

肿瘤细胞固有程序性死亡受体1及其生物学功能研究进展

在肿瘤微环境中,程序性死亡受体1(PD-1)是免疫抑制因子之一,通过与其配体程序性死亡受体配体1(PD-L1)和(或)PD-L2结合后调节淋巴细胞的活化、无能或衰竭等生物学过程.既往的研究中,PD-1只在免疫细胞尤其是功能耗竭的T细胞中表达,通过作用于磷脂酰肌醇-3-羟激酶(PI3K)、蛋白激酶B(AKT)、大鼠肉瘤癌基因(RAS)、促分裂原活化的蛋白激酶(MAPK)/细胞外信号调节激酶(ERK)1/2等相关下游通路导致肿瘤细胞发生免疫逃逸.PD-1在黑色素瘤、肝细胞癌、胰腺癌、结肠癌及非小细胞肺癌等多种肿瘤细胞中固有表达并激活多种信号通路,发挥不同的生物学效应.这些生物学效应均独立于机体的适应性免疫,对肿瘤细胞的增殖发挥促进或抑制作用.目前肿瘤细胞固有PD-1的表达及作用机制尚不明确,但这提示PD-1在肿瘤细胞中的产生和作用机制可能不同于经典的PD-1/PD-L1免疫检查点信号通路,可协助理解PD-1/PD-L1免疫检查点抑制剂在不同肿瘤治疗中疗效不同的可能原因,为补充和完善现有的免疫检查点治疗方案提供重要线索.     

PD-1/PD-L1抑制剂的困境与sPD-1/sPD-L1的标志物潜能

PD-1和PD-L1免疫检查点抑制剂是肿瘤治疗的又一个里程碑,但缺乏灵敏度和特异度高的标志物来筛选对免疫检查点抑制剂敏感的患者,导致在部分癌种和患者中有效率低;而且由于毒副作用和耐药性的存在,进一步限制了其临床应用。可溶性PD-1(sPD-1)和可溶性PD-L1(sPD-L1)是PD-1和PD-L1的溶解形式,已在多种肿瘤中被证实与肿瘤的临床病理特征、分期、疾病的严重程度、治疗敏感性及预后密切相关,可能成为免疫治疗的标志物。全文就PD-1/PD-L1抑制剂的作用机制和其在临床应用中的困境及sPD-1和sPD-L1的标志物潜能进行综述。     

Reconstructed Adeno-Associated Virus with the Extracellular Domain of Murine PD-1 Induces Antitumor Immunity

Background: The negative signaling provided by interactions of the co-inhibitory molecule, programmeddeath-1 (PD-1), and its ligands, B7-H1 (PD-L1) and B7-DC (PD-L2), is a critical mechanism contributing totumor evasion; blockade of this pathway has been proven to enhance cytotoxic activity and mediate antitumortherapy. Here we evaluated the anti-tumor efficacy of AAV-mediated delivery of the extracellular domain ofmurine PD-1 (sPD-1) to a tumor site. Material and Methods: An rAAV vector was constructed in which theexpression of sPD-1, a known negative regulator of TCR signals, is driven by human cytomegalovirus immediateearly promoter (CMV-P), using a triple plasmid transfection system. Tumor-bearing mice were then treated withthe AAV/sPD1 construct and expression of sPD-1 in tumor tissues was determined by semi quantitative RT-PCR,and tumor weights and cytotoxic activity of splenocytes were measured. Results: Analysis of tumor homogenatesrevealed sPD-1 mRNA to be significantly overexpressed in rAAV/sPD-1 treated mice as compared with controllevels. Its use for local gene therapy at the inoculation site of H22 hepatoma cells could inhibit tumor growth, alsoenhancing lysis of tumor cells by lymphocytes stimulated specifically with an antigen. In addition, PD-1 was alsofound expressed on the surfaces of activated CD8+ T cells. Conclusion: This study confirmed that expression ofthe soluble extracellular domain of PD-1 molecule could reduce tumor microenvironment inhibitory effects onT cells and enhance cytotoxicity. This suggests that it might be a potential target for development of therapiesto augment T-cell responses in patients with malignancies.     

Soluble PD-1 facilitates 4-1BBL-triggered antitumor immunity against murine H22 hepatocarcinoma in vivo.

PURPOSE: The use of costimulatory molecules targeting distinct T-cell signaling pathways has provided a means for triggering and enhancing antitumor immunity; however, it is still not fully understood what types of costimulatory molecules are suitable for the combination in tumor therapy. Our purpose in this study is to establish an effective antitumor immune approach by using costimulatory molecule 4-1BBL in combination with soluble PD-1. EXPERIMENTAL DESIGN: The murine H22 hepatocarcinoma served as an ectopic tumor model. Local gene transfer was done by injection with naked plasmid p4-1BBL and/or psPD-1. The synergistic mechanism of dual-gene therapy was elucidated by detecting the change of gene expression of immunoregulatory factors in tumor microenvironment. The effects of immunotherapy were evaluated by testing the function of tumor-specific T cells, measuring tumor weight or volume, survival of mice, and H&E staining of tissues. RESULTS: 4-1BBL expressed by normal nonimmune cells effectively enhanced antitumor immune response but up-regulated PD-L1 and did not reduce IL-10 and transforming growth factor-beta (TGF-beta). sPD-1 synergized with 4-1BBL to establish efficient antitumor immune environment, including down-regulation of IL-10 and TGF-beta, further up-regulation of interleukin (IL)-2 and IFN-gamma, and higher CD8(+) T-cell infiltration. The combined treatment by 4-1BBL/sPD-1 eradicated tumors from mice with small amounts of preexistent tumor cells or tumors from approximately 60% of individuals with larger amounts of preexistent tumor cells. CONCLUSIONS: Our findings in this report imply a great potential of 4-1BBL in combination with sPD-1 in tumor therapeutics with the in vivo existent tumor cells as antigens.     

PD-1/PD-L1 blockade in cancer treatment: perspectives and issues

Recent studies showed that tumor cells ‘edit’ host immunity in several ways to evade immune defenses in the tumor microenvironment. This phenomenon is called “cancer immune escape.” One of the most important components in this system is an immunosuppressive co-signal (immune checkpoint) mediated by the PD-1 receptor and its ligand, PD-L1. PD-1 is mainly expressed on activated T cells, whereas PD-L1 is expressed on several types of tumor cells. Preclinical studies have shown that inhibition of the interaction between PD-1 and PD-L1 enhances the T-cell response and mediates antitumor activity. Several clinical trials of PD-1/PD-L1 signal-blockade agents have exhibited dramatic antitumor efficacy in patients with certain types of solid or hematological malignancies. In this review, we highlight recent clinical trials using anti-PD-1 or anti-PD-L1 antibodies against several types of malignancies, including a trial conducted in our department, and describe the clinical perspectives and issues regarding the PD-1/PD-L1 blockade in cancer treatment.     

Blockade of B7-H1 with sPD-1 improves immunity against murine hepatocarcinoma

BACKGROUND: The B7-H1/PD-1 pathway has been demonstrated to be involved in tumor evasion. In a previous study, we constructed a eukaryotic expression plasmid (pPD-1A), which expresses soluble PD-1 (sPD-1). In this study, the question of whether or not the blockade of B7-H1 with sPD-1 in vivo and vitro can improve antitumor immunity was investigated. MATERIALS AND METHODS: The proliferation of lymphocytes activated by dendritic cells (DCs), which were treated with sPD-1 in vitro, was detected with MTT colorimetry. Mice inoculated with H22 cells were treated by intramuscular injection with pPD-1A. The mRNA expression was analyzed with RT-PCR. RESULTS: The early activation of lymphocytes in vitro was partly improved by sPD-1 blockade. The growth of H22 cells was inhibited significantly after pPD-1A administration. The mRNA expression of 4-1BB, B7.1, IFN-gamma and TNF-alpha of lymphocytes was up-regulated and that of OX40 and IL-10 was down-regulated after pPD-1A administration. CONCLUSION: Blockade of the PD-1/B7-H1 pathway with sPD-1 may be a promising strategy for immunotherapy for hepatocarcinoma. Both cytokines and co-stimulatory molecules of lymphocytes could be regulated by sPD-1 blockade.     

HSP70 vaccine in combination with gene therapy with plasmid DNA encoding sPD-1 overcomes immune resistance and suppresses the progression of pulmonary metastatic melanoma

Many tumor immunotherapy efforts are focused on the generation of strong T-cell response against tumor antigens. However, strong T-cell response does not always coincide with tumor rejection, for which upregulated expression of immunoinhibitory molecules may be responsible. In this study, the treatment with heat shock protein 70 (HSP70) vaccine induced an infiltration of T cells into the tumor site as well as the expression of IFN-gamma and IL-2, and delayed lung metastases of tumor, but the tumor progression nonetheless occur finally. We demonstrated that B7-H1 expressed by residual tumor cells was responsible for the resistance of tumor to the therapy with HSP70 vaccine. Blockade of B7-H1 by i.v. injection pPD-1A, a plasmid encoding the extracellular domain of PD-1 (sPD-1), could reverse this resistance and enhance the therapeutic efficacy. To complement these findings, we investigated the gene expression of tumor-infiltrating lymphocytes (TILs) by Real-time PCR analysis, which revealed that the expression of TH1 cytokines IFN-gamma and IL-2 by TIL in the mice treated with HSP70 vaccine in combination with sPD-1 was increased and the expression of negative regulatory molecules IL-10, TGF-beta and foxp3 was decreased, demonstrating that multifunctional properties afforded by the combination therapy can effectively overcome tumor resistance and promote effective antitumor immunity. The in vivo transfection with pPD-1A could be performed as infrequently as once a week and still produce a significant antitumor effect. These findings suggest that the treatment with HSP70 vaccine followed by blockade of tumor-B7-H1 with sPD-1 may provide a promising approach for tumor immunotherapy.     

PD-1/PD-L1通路在髓系肿瘤中的研究进展

在免疫系统中,为防止免疫反应过度,细胞表面会有抑制免疫反应的检查点,其中程序性死亡受体-１(programmed death-1,PD-1)与其程序性死亡配体-1(programmed death-ligand 1,PD-L1）就是其中的一对免疫检查点,肿瘤细胞通过表达PD-L1与免疫细胞上的PD-1受体结合,使得肿瘤细胞可以逃避免疫细胞的攻击。研究表明,PD-1及PD-L1在多种实体肿瘤组织及免疫细胞中存在过表达现象,导致抗肿瘤细胞功能消失,并且与不良预后相关,但在髓系肿瘤中的研究较少。因此本文从PD-1/PD-L1的生物学特点,目前在髓系肿瘤中的表达情况,以及传统化疗药物对该通路的作用作一综述,旨在为髓系肿瘤的诊疗提供新的靶点。     

PD-1/PD-L1通路在乳腺癌治疗中的作用及意义

程序性死亡受体1（programmed death-1,PD-1,CD279）为共刺激受体CD28超家族成员,主要表达在活化T细胞、B细胞、单核细胞以及自然杀伤细胞表面。程序性死亡配体1（programmed death-ligand 1,PD-L1,CD274）为PD-1的一个重要配体,广泛表达于肿瘤细胞以及抗原呈递细胞（APC）表面。以PD-1/PD-L1为靶点的肿瘤免疫治疗为肿瘤治疗开辟了新的道路。PD-1通过与PD-L1和(或)PD-L2结合,抑制T细胞活化,诱导T细胞凋亡,在肿瘤免疫逃逸中起着重要的作用。目前PD-1/PD-L1信号通路成为免疫靶向治疗的新靶点,相关研究在非小细胞肺癌、晚期黑色素瘤等多种恶性肿瘤领域有重大进展,研究发现PD-L1 在多种肿瘤细胞包括乳腺癌中表达上调,提示 PD-1/PD-L1通路可能参与肿瘤的免疫逃逸。本文将针对PD-1/PD-L1通路在乳腺癌治疗中的作用及意义进行综述。     

PD-1/PD-L1抑制剂在前列腺癌免疫治疗中的研究进展

前列腺癌（prostate cancer,PCa）发病率呈逐年上升趋势,前列腺癌免疫治疗已成为继外科、放疗、化疗之后的第四种治疗方法。作为当今肿瘤免疫治疗领域最具有研究前景的免疫检查点抑制剂中的程序性死亡受体-1（programmed cell death-1,PD-1）/程序性死亡配体-1（programmed cell death-ligand1,PD-L1）抑制剂,通过阻断PD-1与其配体PD-L1结合,从而终止T细胞的负性调控信号,使T细胞的活性恢复,进而逆转肿瘤免疫逃逸机制,恢复自身免疫应答,最后起到抑制和杀伤肿瘤的作用。本文就目前应用于前列腺癌临床试验的PD-1/PD-L1抑制剂的现况和临床疗效研究进展进行综述。      

Casp8 acts through A20 to inhibit PD-L1 expression: The mechanism and its implication in immunotherapy

Immunotherapy targeting the PD-L1/PD-1 pathway is a novel type of clinical cancer treatment, but only small subsets of patients can benefit from it because of multiple factors. PD-L1/PD-1 expression is a biomarker for predicting the efficacy of anti-PD-L1/PD-1 therapy, which highlights the importance of understanding the regulatory mechanisms of PD-L1 expression in cancer cells. Casp8 is an apical caspase protease involved in mediating cell apoptosis, but it also has multiple nonapoptotic functions. Casp8 mutations are associated with increased risks of cancer, and low expression of Casp8 is closely connected with poor prognosis in patients with cancer. In addition, mutations of Casp8 in lymphocytes also lead to human immunodeficiency, thereby causing dysfunction of the innate immune system, but the roles of Casp8 in antitumor immunity remain unclear. Here, we found that knocking down Casp8 in mouse melanoma cells promoted tumor progression in an immune system–dependent manner. Mechanistically, Casp8 induced PD-L1 degradation by upregulating TNFAIP3 (A20) expression, a ubiquitin-editing enzyme that results in PD-L1 ubiquitination. In addition, compared with Casp8^fl/fl mice, mice with conditional deletion of Casp8 in natural killer (NK) cells (Ncr1^iCre/+Casp8^fl/fl mice) showed a decreased frequency of IFN-γ+ and CD107a+ NK cells but an increased frequency of PD-1+ and CTLA-4+ NK cells. Melanoma cells with Casp8 knocked down exhibited sensitivity to anti-PD-1 or anti-CTLA-4 antibody treatments, particularly in Ncr1iCre/+Casp8fl/fl mice. Together, the results indicate that Casp8 induces PD-L1 degradation by upregulating A20 expression and that decreased Casp8 expression is a potential biomarker for predicting the sensitivity to anti-PD-L1/PD-1 immunotherapy.