靶向CD47 抗肿瘤治疗的研究进展

[摘要] CD47 是细胞表面高度糖化的穿膜蛋白，是一种“别吃我”信号，可与信号调节蛋白α（SIRPα）等形成CD47-SIRPα 抑制信号复合体，从固有免疫和适应性免疫两方面同时逃避机体的免疫监视。研究发现，CD47 在血液肿瘤和多种实体瘤中高表达，通过与巨噬细胞上的SIRPα 配体结合，启动一系列抑制性的信号转导而躲避吞噬，其高水平表达既能促进肿瘤细胞的生长又能促进肿瘤细胞的转移。通过抗CD47 抗体阻断CD47-SIRPα 信号通路，达到抑制肿瘤细胞的免疫逃逸，增强巨噬细胞的吞噬作用和适应性免疫应答，是免疫治疗肿瘤的新途径。目前，国内外开展了越来越多靶向CD47-SIRPα 的药物或抗体的基础研究和临床试验，有望从抗体分子设计和重组蛋白等方面解决靶向CD47 抗肿瘤治疗时发生的贫血和输液相关不良反应等问题。本文就CD47 的分子结构与生理功能、CD47-SIRPα 表达调控机制、CD47 抗肿瘤治疗研究现状以及靶向CD47 导致的相关生物安全性问题和解决方案等方面进行综述，为CD47新靶点的基础研究和临床应用提供参考。     

天然免疫检查点CD47-SIRPα在恶性肿瘤中的研究进展

针对CTLA-4/B7和PD-1/PD-L1的免疫检查点抑制剂现已广泛应用于临床,其他检查点抑制剂也正在开发中。CD47是广泛表达于正常细胞表面的蛋白质,在肿瘤细胞中呈过表达状态,其受体为髓系抑制性免疫受体SIRPα。阻断CD47与SIRPα之间的相互作用可增强巨噬细胞和中性粒细胞的吞噬作用进而消灭肿瘤细胞。此外,越来越多的证据表明阻断CD47-SIRPα轴还可以增强抗原呈递细胞的功能,从而刺激T细胞介导的抗癌免疫。随着该领域研究的发展,CD47-SIRPα轴的临床应用将会是未来肿瘤免疫治疗的热点之一。     

抗CD47单克隆抗体制备及其促巨噬细胞吞噬作用鉴定

目的:制备可识别肿瘤细胞表达CD47蛋白的抗CD47单克隆抗体,并鉴定其抗肿瘤作用。方法:利用BL21(DE3)原核表达系统表达CD47胞外段蛋白,利用Ni-NTA层析纯化表达蛋白。免疫BALB/c小鼠,制备并筛选分泌抗CD47单克隆抗体的杂交瘤细胞株。利用正辛酸-硫酸铵沉淀方法纯化抗CD47单抗。利用流式细胞术检测纯化抗体的活性。利用巨噬细胞与肿瘤细胞共培养试验,检测抗CD47单抗的抗肿瘤作用。结果:表达并纯化了CD47胞外段蛋白,筛选到了分泌抗CD47单克隆抗体的杂交瘤细胞株—7D4,流式细胞术检测结果显示,抗体具有结合肿瘤细胞的活性,但是对不同肿瘤类型细胞的结合效率存在差异。巨噬细胞与肿瘤细胞共培养试验发现,利用抗体封闭肿瘤细胞CD47信号后,可以增强巨噬细胞对肿瘤细胞的吞噬作用。结论:抗CD47单抗—7D4可以促进巨噬细胞的吞噬作用,具有潜在应用价值。     

抗CD47靶向治疗研究现状及应用前景

在肿瘤发生发展过程中,肿瘤细胞逃逸了免疫系统的监视;免疫逃逸机制对于研发新的抗肿瘤治疗方案具有重要的意义。免疫治疗旨在激活患者自身的免疫系统,是肿瘤治疗相关研究的前沿,具有广阔的应用前景。CD47是一种广泛表达的细胞表面分子,肿瘤细胞可能借此“别吃我”信号,逃避了肿瘤免疫;肿瘤干细胞中CD47的表达水平甚至比肿瘤细胞更高。通过使用抗CD47抗体阻断CD47-SIRPα通路,从而介导细胞吞噬作用,能够靶向性杀伤肿瘤细胞。现在多项关于CD47靶向治疗的临床试验正在进行中,包括两种单克隆抗体和一种融合蛋白。然而由于使用动物模型不一,可能高估了这些药物的临床疗效预测。现将CD47抗肿瘤治疗相关研究的背景及潜在问题加以综述,并对该治疗的未来应用前景予以展望。      

CD47在淋巴瘤治疗中的研究进展

CD47作为一种跨膜蛋白,广泛分布于多种细胞,通过与巨噬细胞上信号调节蛋白α（SIRPα）结合,释放抑制信号,逃避巨噬细胞的吞噬。淋巴瘤细胞CD47表达上调是诱导免疫逃逸的重要机制之一,也是潜在的治疗靶点。文章就CD47诱导的免疫逃逸、靶向CD47的单克隆抗体和细胞免疫治疗等治疗手段在淋巴瘤治疗中的研究进展进行综述。     

靶向CD47的抗肿瘤抗体研究进展

CD47是个多能分子,在肿瘤细胞逃避免疫监视过程中扮演重要角色,阻断CD47信号通道能有效激发巨噬细胞对肿瘤细胞的吞噬作用,成为非常有前景的肿瘤免疫治疗新途径。靶向CD47的单克隆抗体已成为近年来研究的新热点,目前的实验进展顺利,有必要进行更详尽的研究,使其早日进入临床应用。     

CD47与胰腺癌相关性的研究进展

CD47分子是一种高度糖化的跨膜蛋白,存在于所有组织的多种细胞表面上。近几年的研究表明,CD47分子与多种恶性肿瘤密切相关,在大部分肿瘤细胞中呈现高表达,它与特异性配体结合后,可对免疫细胞吞噬肿瘤细胞产生抑制作用,使其产生免疫逃逸,故可促进肿瘤的发生与发展。胰腺癌是常见的消化系统肿瘤,恶性程度极高,诊断、治疗困难,预后不理想。与其他肿瘤类似,胰腺肿瘤与人体免疫系统之间也存在一定相关性,但CD47与胰腺癌相关性的研究甚少,故本文将从CD47的分子结构、生理功能、表达情况及与胰腺癌的相关性进行综述,并对胰腺癌的免疫治疗进行总结和展望。     

CD47在肿瘤中的表达及治疗应用

近年来研究发现,CD47通过上调在肿瘤细胞表面的表达来影响肿瘤的生长与转移,同时,其表达上调预示临床预后较差;而CD47单抗可通过激活适应性免疫及直接介导细胞凋亡等机制抑制肿瘤生长.此外,CD47还具有调节血液系统和胃肠道系统正常组织细胞的放射性损伤修复作用,有望成为肿瘤治疗的新靶点.     

膜结合型巨噬细胞集落刺激因子对巨噬细胞功能性极化影响的探索

 目的　探讨高表达膜结合型巨噬细胞集落刺激因子（mM-CSF）的血液肿瘤细胞对巨噬细胞的异常活化作用。方法　采用稳定表达mM-CSF的淋巴瘤细胞系Namalwa-M和巨噬细胞系RAW264.7体外共培养体系,以转入空载体的Namalwa-V细胞系共培养体系为对照组。流式细胞术检测RAW264.7的CD206（选择性活化巨噬细胞高表达的表面分子）和细胞内白细胞介素（IL）-6、IL-10、IL-12及TNF-α的表达水平;墨汁吞噬实验检测共培养RAW264.7细胞的功能变化。 结果　与Namalwa-M共培养的RAW264.7 的CD206表达水平明显升高平均均荧光强度为55.12±3.77,提示其巨噬细胞活性增强;IL-10、TNF-α表达上调（201±6）%、（136±6）%;IL-12、IL-6表达下调（990±528）%、（60±26）%;吞噬能力明显提高。结论　高表达mM-CSF的血液肿瘤细胞可异常活化巨噬细胞成为高表达IL-10、TNF-α,低表达IL-12、IL-6的异常活化巨噬细胞。     

SLAMF7-SLAMF7信号通路在肿瘤进展中的作用及相关机制CSCD

信号淋巴细胞激活分子成员7(SLAMF7)不仅表达于多种肿瘤细胞表面,也表达于众多免疫细胞中,如自然杀伤细胞、CD4+T细胞、CD8+T细胞、B细胞、树突状细胞、单核/巨噬细胞等,并参与调控肿瘤微环境中肿瘤细胞及免疫细胞的增殖、黏附、生长及分化,最终影响着免疫细胞的抗肿瘤作用。本文将对SLAMF7调控免疫细胞抑制肿瘤细胞功能的研究现状进行综述。     

CD47 blockade inhibits tumor progression human osteosarcoma in xenograft models

Osteosarcoma is the most common bone tumors in children and adolescents. Despite intensive chemotherapy, patients with advanced disease still have a poor prognosis, illustrating the need for alternative therapies. In this study, we explored the use of antibodies that block CD47 with a tumor growth suppressive effect on osteosarcoma. We first found that up-regulation of CD47 mRNA levels in the tumorous tissues from eight patients with osteosarcoma when compared with that in adjacent non-tumorous tissues. Further western-blot (WB) and immunohistochemistry (IHC) demonstrated that CD47 protein level was highly expressed in osteosarcoma compared to normal osteoblastic cells and adjacent non-tumorous tissues. Osteosarcoma cancer stem cell markers staining shown that the majority of CD44⁺ cells expressed CD47 albeit with different percentages (ranging from 80% to 99%). Furthermore, high CD47 mRNA expression levels were associated with a decreased probability of progression-free and overall survival. In addition, blockade of CD47 by specific Abs suppresses the invasive ability of osteosarcoma tumor cells and further inhibits spontaneous pulmonary metastasis of KRIB osteosarcoma cells in vivo. Finally, CD47 blockade increases macrophage phagocytosis of osteosarcoma tumor cells. In conclusion, our findings demonstrate that CD47 is a critical regulator in the metastasis of osteosarcoma and suggest that targeted inhibition of this antigen by anti-CD47 may be a novel immunotherapeutic approach in the management of this tumor.     

抗CD47单克隆抗体对卵巢癌细胞靶向治疗的体外研究

  目的   探讨抗CD47单克隆抗体在体外对巨噬细胞吞噬卵巢癌细胞作用的影响。  方法   收集天津医科大学附属肿瘤医院2011年6月至2011年12月手术切除的卵巢组织样本45例(包含卵巢癌组织样本39例, 正常卵巢组织样本6例), 获得的组织细胞通过流式细胞术分析CD47的表达水平, 通过细胞功能学实验观察抗CD47单克隆抗体在体外对小鼠巨噬细胞吞噬卵巢癌细胞的靶向治疗作用。  结果   流式细胞术分析显示, 卵巢癌细胞系SKOV-3细胞和卵巢癌组织细胞中CD47表达水平均明显高于正常人卵巢上皮细胞, 差异具有统计学意义(P < 0.01), 且与疾病的分化程度相关(P < 0.05)。细胞功能学实验结果显示, 抗CD47单克隆抗体在体外可促进巨噬细胞对卵巢癌细胞的吞噬作用, 各实验组(1μg/mL、5μg/mL、10μg/mL、20μg/mL)分别较空白对照组吞噬指数显著增加, 并且随抗体浓度的增加吞噬指数呈浓度依赖性, 差异均具有统计学意义(P < 0.01)。统计学分析显示, 10μg/mL浓度组吞噬指数达到峰值, 同20μg/mL浓度组吞噬指数无显著性差异(P > 0.05)。  结论   CD47高表达于卵巢癌组织细胞, 且与组织分化程度相关。抗CD47单克隆抗体在体外可促进巨噬细胞对卵巢癌肿瘤细胞的吞噬作用, 为卵巢癌的靶向治疗提供了实验依据。      

CD47‐signal regulatory protein α signaling system and its application to cancer immunotherapy

Tumor cells evade immune surveillance through direct or indirect interactions with various types of immune cell, with much recent attention being focused on modifying immune cell responses as the basis for the development of new cancer treatments. Signal regulatory protein α (SIRPα) and CD47 are both transmembrane proteins that interact with each other and constitute a cell‐cell communication system. SIRPα is particularly abundant in myeloid cells such as macrophages and dendritic cells, whereas CD47 is expressed ubiquitously and its expression level is elevated in cancer cells. Recent studies have shown that blockade of CD47‐SIRPα interaction enhances the phagocytic activity of phagocytes such as macrophages toward tumor cells in vitro as well as resulting in the efficient eradication of tumor cells in a variety of xenograft or syngeneic mouse models of cancer. Moreover, CD47 blockade has been shown to promote the stimulation of tumor‐specific cytotoxic T cells by macrophages or dendritic cells. Biological agents, such as Abs and recombinant proteins, that target human CD47 or SIRPα have been developed and are being tested in preclinical models of human cancer or in clinical trials with cancer patients. Preclinical studies have also suggested that CD47 or SIRPα blockade may have a synergistic antitumor effect in combination with immune checkpoint inhibitors that target the adaptive immune system. Targeting of the CD47‐SIRPα signaling system is thus a promising strategy for cancer treatment based on modulation of both innate and acquired immune responses to tumor cells.     

Enhancement of epidermal growth factor receptor antibody tumor immunotherapy by glutaminyl cyclase inhibition to interfere with CD47/signal regulatory protein alpha interactions

Integrin associated protein (CD47) is an important target in immunotherapy, as it is expressed as a “don't eat me” signal on many tumor cells. Interference with its counter molecule signal regulatory protein alpha (SIRPα), expressed on myeloid cells, can be achieved with blocking Abs, but also by inhibiting the enzyme glutaminyl cyclase (QC) with small molecules. Glutaminyl cyclase inhibition reduces N-terminal pyro-glutamate formation of CD47 at the SIRPα binding site. Here, we investigated the impact of QC inhibition on myeloid effector cell-mediated tumor cell killing by epidermal growth factor receptor (EGFR) Abs and the influence of Ab isotypes. SEN177 is a QC inhibitor and did not interfere with EGFR Ab-mediated direct growth inhibition, complement-dependent cytotoxicity, or Ab-dependent cell-mediated cytotoxicity (ADCC) by mononuclear cells. However, binding of a human soluble SIRPα-Fc fusion protein to SEN177 treated cancer cells was significantly reduced in a dose-dependent manner, suggesting that pyro-glutamate formation of CD47 was affected. Glutaminyl cyclase inhibition in tumor cells translated into enhanced Ab-dependent cellular phagocytosis by macrophages and enhanced ADCC by polymorphonuclear neutrophilic granulocytes. Polymorphonuclear neutrophilic granulocyte-mediated ADCC was significantly more effective with EGFR Abs of human IgG2 or IgA2 isotypes than with IgG1 Abs, proposing that the selection of Ab isotypes could critically affect the efficacy of Ab therapy in the presence of QC inhibition. Importantly, QC inhibition also enhanced the therapeutic efficacy of EGFR Abs in vivo. Together, these results suggest a novel approach to specifically enhance myeloid effector cell-mediated efficacy of EGFR Abs by orally applicable small molecule QC inhibitors.     

肿瘤坏死因子CD70在肿瘤发生与治疗中的研究进展

CD70是肿瘤坏死因子(TNF)超家族的成员之一，是一种Ⅱ型跨膜蛋白，在调控免疫应答过程中发挥重要的作用。CD70的高表达常见于多种肿瘤组织中，目前以CD70为靶点的免疫治疗药物已经在临床前期研究中应用。CD70在肿瘤细胞表面的表达，不仅可使肿瘤细胞逃避免疫监视、诱导免疫细胞凋亡，同时也可以激活部分免疫细胞杀伤肿瘤细胞，这些作用给恶性肿瘤的免疫治疗带来了新的方向。本文就近年来CD70在肿瘤研究中的进展作一综述。     

CD47: a potential immunotherapy target for eliminating cancer cells

The relationship between the immune system and cancer growth and aggravation has been discussed over a century. A number of molecules have been shown to participate in this process. CD47, a normal universally expressed member of the immunoglobulin superfamily, plays multiple functions in immune system. Researches demonstrated that CD47 was also highly expressed on the surface of tumor cells as well as cancer stem cells (CSCs). Whether the highly expressed CD47 was associated with tumor growth, metastasis, recurrence, or drug resistance has become the hotspot. Besides the roles of CD47 in tumor immunoregulation, the monoclonal antibodies targeting CD47 used in acute myelogenous leukemia (AML) and bladder CSCs were reported, which shed new light on tumor treatment. CSCs have been recognized as the root of tumor drug resistance and recurrence. Whether CD47 on CSCs could serve as a potential target for future anti-cancer treatment forms the focus of our review. Here we highlight the potential roles of CD47 in immune system, and discuss the promising therapeutic application of anti-CD47 antibodies for eliminating tumor cells.     

Combination of CD47 and signal‐regulatory protein‐α constituting the “don’t eat me signal” is a prognostic factor in diffuse large B‐cell lymphoma

The interaction between CD47 and signal‐regulatory protein‐α (SIRPα) inhibits phagocytosis, thus affecting the clinical outcomes of neoplastic diseases. Although CD47 upregulation is associated with poor prognosis in several malignancies, the effect of SIRPα expression and its coexpression with CD47 remains unclear. This study aimed to investigate the clinicopathologic effect of CD47 and SIRPα expression in diffuse large B‐cell lymphoma (DLBCL). Immunostaining of 120 biopsy samples showed that CD47 is primarily expressed in tumor cells, whereas SIRPα is expressed in nonneoplastic stromal cells, mostly macrophages. CD47^high cases showed higher MYC protein expression and lower MYC translocation. The SIRPα^high cases presented significantly shorter overall survival (OS) and progression‐free survival (PFS) than SIRPα^low cases in the activated B‐cell (ABC) subtype of DLBCL (P = .04 and P = .02, respectively). Both CD47^high and SIRPα^high presented significantly shorter OS and PFS than other cases among all DLBCL patients (P = .01 and P = .004, respectively), and the ABC type (P = .04 and P = .008, respectively) but not the germinal center B‐cell type. Both CD47^high and SIRPα^high yielded a constant independent prognostic value for OS and PFS in multivariate analysis (hazard ratio [HR], 2.93; 95% confidence interval [CI], 1.20‐7.43; P = .02; and HR, 2.87; 95% CI, 1.42‐5.85; P = .003, respectively). To the best of our knowledge, this is the first study to report that combinatorial CD47 and SIRPα expression is a potential independent prognostic factor for DLBCL. Evaluation of CD47 and SIRPα expression could be useful before CD47 blockade therapy.