补体调节蛋白CD59与肿瘤

作为补体终末阶段调节蛋白的CD59分子在多种实体瘤细胞表面高表达.高表达的CD59分子能够阻断补体激活途径降低补体系统对肿瘤细胞的溶解杀伤作用,最终导致肿瘤细胞逃避机体免疫监视.研究利用单克降抗体、细胞因子等抑制CD59的抗补体活性可在肿瘤免疫治疗中取得一定的疗效.     

补体调节蛋白CD 46、CD 55和CD 59在胃肠肿瘤中的研究进展

胃肠肿瘤细胞的细胞膜高表达补体调节蛋白（complement regulatory proteins，CRPs）中的一种或几种分子。这些高表达分子可抑制机体的体液免疫和细胞免疫，可能是导致肿瘤细胞逃避机体免疫监视的机制之一。近年来许多学者在研究CRPs在胃肠肿瘤中的表达及其作用机制，以及将CRPs相关的单克隆抗体（monoclonal antibodies，McAbs）应用于肿瘤免疫治疗，取得了一定疗效。本文将CRPs在胃肠肿瘤研究中所取得的进展作一综述。     

人CD46、CD55和CD59与肿瘤免疫逃逸及免疫治疗

膜结合补体调节蛋白CD46、CD55和CD59在肿瘤细胞膜上表达或过表达,保护肿瘤细胞免受免疫系统的攻击,成为肿瘤细胞免疫逃逸的途径之一.如何下调肿瘤细胞表面三者表达或抑制其功能以增强其对补体依赖的细胞毒作用的敏感性备受关注.     

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。     

CD47与淋巴瘤免疫治疗相关性的研究进展

CD47属于免疫球蛋白超家族成员,在人体多种细胞和组织上均有表达,但在肿瘤细胞上表达得更多,特别是在各种造血系统肿瘤中高表达。肿瘤细胞上表达的CD47与巨噬细胞上的信号调节蛋白α（SIRPα）结合抑制巨噬细胞对肿瘤的吞噬作用可导致肿瘤免疫逃逸。近年来CD47成为肿瘤研究的新热点,本文就CD47的结构与表达、CD47-SIRPα、靶向CD47抗体药物与淋巴瘤免疫治疗相关性研究作一综述。     

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。     

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。      

CD4＋CD25＋Foxp3＋Treg细胞调控肿瘤免疫抑制微环境的研究进展

目的： CD4＋CD25＋Foxp3＋调节性T细胞（ Treg ）是肿瘤免疫抑制微环境的主要组成部分,其在肿瘤的免疫抑制微环境中分泌IL－10、IL－35、TGF－β1和FGL2等细胞因子发挥免疫抑制作用。Treg细胞抑制CD4＋T、CD8＋T淋巴细胞和NK细胞,进而抑制特异性抗肿瘤免疫反应使肿瘤细胞更容易逃避免疫监视。进一步研究Treg细胞在肿瘤免疫中的作用机制,对深入了解恶性肿瘤的发病机制及免疫治疗具有重要的理论意义。此外,Treg细胞及其分泌的细胞因子在肿瘤治疗和预后评估等方面也具有广阔的临床应用前景。     

CD200在恶性肿瘤作用中的研究进展

肿瘤免疫治疗是肿瘤治疗中一种非常有前景的治疗手段，包括主动免疫治疗、过继细胞转移治疗和免疫检查点阻断治疗。CD200作为一种免疫耐受信号分子，在维持机体自身免疫耐受中发挥重要作用。近年来，研究显示免疫检查点CD200及其受体CD200R在多种肿瘤中异常表达，且与肿瘤的侵袭、转移及患者预后不良相关，此外CD200/CD200R过度激活在抑制抗肿瘤免疫应答中发挥重要作用，这展现了其在肿瘤免疫治疗中的潜力。本文就CD200的结构、生物学功能及其在肿瘤免疫治疗前景的研究进展进行综述。     

抗肿瘤血管生成的新策略——组织因子靶向免疫治疗

一种以组织因子为靶向的免疫结合物（icon），可以选择性地结合肿瘤血管内皮细胞及某些肿瘤细胞异常表达的组织因子，并通过Fe受体和补体，启动机体免疫系统以及攻击肿瘤血管或肿瘤细胞，与此同时，正常血管内皮细胞因不表达组织因子子而免受损害，是一种具有广谱抗肿瘤免疫治疗的新方法。     

Decay accelerating factor (CD55): a target for cancer vaccines?

The 791Tgp72 antigen has been used successfully as a target for tumor imaging and T-cell immunotherapy. We have characterized this antigen using the monoclonal antibody 791T/36 as a 72/66 kDa doublet. NH2-terminal protein sequencing of the two bands revealed identity with the complement regulatory protein CD55. Antibodies recognizing different domains of CD55 were also shown to bind to the purified 791Tgp72, although sequence analysis of the cDNA cloned from 791T tumor cells showed 100% homology with CD55 and transfection of the cDNA into antigen-negative CHO cells resulted in binding of 791T/36. This identifies the tumor antigen 791Tgp72 as CD55. This protein protects cells from complement attack; however, it can also transduce signals in lymphocytes and is a ligand for CD97, expressed by activated T cells. These results suggest that CD55 plays a role in signaling between the innate and adaptive immune responses. It is therefore a very intriguing target, because absence of the molecule makes the tumor cells susceptible to complement, whereas protective overexpression results in the antigen being a target for T-cell immunotherapy.     

Lipoplex mediated silencing of membrane regulators (CD46, CD55 and CD59) enhances complement-dependent anti-tumor activity of trastuzumab and pertuzumab

The therapeutic potential of anticancer antibodies is limited by the resistance of tumor cells to complement-mediated attack, primarily through the over-expression of membrane complement regulatory proteins (mCRPs: CD46, CD55 and CD59). Trastuzumab, an anti- HER2 monoclonal antibody, approved for the treatment of HER2-positive breast and gastric cancers, exerts only minor complement-mediated cytotoxicity (CDC). Pertuzumab is a novel anti-HER2 monoclonal antibody, which blocks HER2 dimerization with other ligand-activated HER family members. Here, we explored the complement-mediated anti-tumor effects of trastuzumab and pertuzumab on HER2-positive tumor cells of various histological origins.Delivery of chemically stabilized anti-mCRP siRNAs using cationic lipoplexes, AtuPLEXes, to HER2-over-expressing BT474, SK-BR-3 (breast), SKOV3 (ovarian) and Calu-3 (lung) cancer cells reduced mCRPs expression by 85–95%. Knockdown of individual complement regulators variably led to increased CDC only upon combined treatment with trastuzumab and pertuzumab. The combined down-regulation of all the three regulators augmented CDC by 48% in BT474, 46% in SK-BR-3 cells, 78% in SKOV3 cells and by 30% in Calu-3 cells and also increased complement-induced apoptosis and caspase activity on mCRP neutralized tumor cells. In addition, antibody-induced C3 opsonization of tumor cells was significantly enhanced after mCRP silencing and further augmented tumor cell killing by macrophages.Our findings suggest that siRNA-induced inhibition of complement regulator expression clearly enhances complement- and macrophage-mediated anti-tumor activity of trastuzumab and pertuzumab on HER2-positive tumor cells. Thus – if selectively targeted to the tumor – siRNA-induced inhibition of complement regulation may serve as an innovative strategy to potentiate the efficacy of antibody-based immunotherapy.     

Amphiregulin activates regulatory T lymphocytes and suppresses CD8+ T cell-mediated anti-tumor response in hepatocellular carcinoma cells

CD8⁺ T cell-mediated immune response plays an important role in inhibiting progression of hepatocellular carcinoma (HCC). For strategic immunotherapy, it is critical to understand why some of the tumor cells escape from this immune attack. In this study, we investigated how HCC cells alter endogenous anti-tumor immunity and their related signaling pathways. We found that HCC cells, both in vitro and in vivo, substantially secret and express amphiregulin (AR). AR in turn activates immunosuppressive function of intratumoral CD4⁺Foxp3⁺ regulatory T cells (Tregs), a major inhibitor of CD8⁺ T cells. Using either lentiviral siRNA, or AR neutralizing antibody, we blocked the expression and function of AR to test the specificity of AR mediated activation of Tregs, Biochemical and cell biology studies were followed and confirmed that blocking of AR inhibited Tregs activation. In addition, we found that AR can trigger the activation of rapamycin complex 1(mTORC1) signaling in Tregs. The mTORC1 inhibitor rapamycin treatment led to compromise Treg function and resulted in enhancing anti-tumor function of CD8⁺ T cells. Blocking AR/EGFR signaling in Tregs with Gefitinib also enhanced anti-tumor immunity and decreased tumor size in a mouse xenograft tumor model. Taken together, our study suggested a novel mechanism of functional interaction between HCC and Tregs for regulating anti-tumor function of CD8⁺ T cells.     

CD40 ligand immunotherapy in cancer: an efficient approach

Cancer cells do not elicit a clinically sufficient anti-tumor immune response that results in tumor rejection. Recently, many investigators have been trying to enhance anti-tumor immunity and encouraging results have been reported. This review will discuss current anti-cancer immunotherapy; interleukin-2 therapy, tumor vaccine secreting Granulocyte macrophage-colony stimulating factor, dendritic cells fused with tumor cells, and CD40 ligand immunotherapy. Moreover, we introduce our two kinds of CD40 ligand immuno-genetherapy; (1) oral CD40 ligand gene therapy against lymphoma using attenuated Salmonella typhimurium (published in BLOOD 2000), (2) cancer vaccine transfected with CD40 ligand ex vivo for neuroblastoma (unpublished). Both approaches resulted in a high degree of protection against the tumor progression and they are simple and safe in the murine system.     

CD276 suppresses CAR-T cell function by promoting tumor cell glycolysis in esophageal squamous cell carcinoma

BackgroundAs an immune checkpoint that suppresses antitumor immunity, CD276 is a potential therapeutic target for cancer immunotherapy. However, the role of CD276 in esophageal squamous cell carcinoma (ESCC) has not been thoroughly examined. A greater understanding of the regulatory mechanism of CD276 may improve the clinical response and efficacy of cancer immunotherapy.MethodsThe expression of CD276 was measured by qRT-PCR, IHC and flow cytometry analysis. T cell infiltration in ESCC was measured by qRT-PCR and immunofluorescence analysis. The regulation function of CD276 in glucose metabolism was examined by metabolism assays, western blotting and small molecule inhibitors. Transfection was used for gene editing. The oncogenic function of CD276 was examined in vivo by CAR-T cell therapy model.ResultsBased on our findings, CD276 regulated the expression of the PKM2 gene in ESCC. Overexpression of CD276 induced the phosphorylation of PKM2 by the STAT3 signalling pathway to promote glucose metabolism in tumors. The accumulation of lactic acid in the tumor microenvironment has been reported to regulate the immune cells, particularly CD8+ T cells. We further analyzed the effect of CD276 on the function of T cells. Chimeric antigen receptor T cells (CAR-T) targeting human epidermal growth factor receptor 2 (HER2) were used as effector cells to detect the effect of CD276 on immunotherapy. The therapeutic effects of CAR-T cells were markedly limited by CD276 overexpression.ConclusionsOur results are the first to show that tumor-derived CD276 supports disease progression. Overexpression of CD276 promoted glucose metabolism in tumor and inhibited the function of CD8+ T cells. Therefore, strategies targeting CD276 might improve the response to cancer immunotherapy of ESCC patients.     

Expression of complement regulatory proteins: CD46, CD55, and CD59 and response to rituximab in patients with CD20(+) non-Hodgkin’s lymphoma

Rituximab is an anti-CD20 humanized monoclonal antibody widely used in the treatment of B-cell non-Hodgkin’s lymphomas (NHLs). Its mechanism of action is related with complement function—complement mediated cytotoxicity. CD46, CD55, and CD59 are complement regulatory proteins. The aim of this study was to analyze expression of complement inhibitors CD46, CD55, and CD59 in patients with CD20(+) NHLs treated with rituximab combined with chemotherapy. A total of 27 patients with CD20(+) NHLs were evaluated (13 females and 14 males). The median age of patients was 56 years. All patients were examined before treatment with rituximab. Expression of CD46, CD55, and CD59 was determined by two-color flow cytometry. A total of 15 patients achieved complete response (CR), 5 patients achieved partial response, and 7 patients had no or minimal response (NR) after rituximab therapy. We observed that expression of CD46 and CD59 were higher in patients with CR than in group with NR. Expression of CD55 and CD59 were higher in patients with bulky disease. In conclusion level of expression of CD46, CD55, and CD59 could be clinically helpful to predict the response to rituximab therapy.     

K562 erythroleukemic cells are equipped with multiple mechanisms of resistance to lysis by complement

Resistance of tumor cells to lysis by complement is generally attributed to several protective mechanisms. The relative impact of these mechanisms in the same tumor cell, however, has not been assessed yet. We have analyzed the interaction of the human erythroleukemia tumor cell line K562 with human complement. K562 cells express the membrane complement regulatory proteins CD59, CD55 and CD46. As shown here for the first time, K562 also spontaneously release the soluble regulators C1 inhibitor, factor H, and soluble CD59. Complement resistance of K562 cells is augmented upon treatment with PMA, TNF or even with sublytic complement. Unlike TNF and sublytic complement, PMA enhanced the expression of membrane-bound CD55 and CD59 and led to increased secretion of soluble CD59. In addition, we show that complement-resistant K562 cells express a membrane-associated proteolytic activity, higher than the complement-sensitive K562/S cells. Treatment of complement-resistant K562 cells with serine protease inhibitors enhance their sensitivity to complement-mediated lysis. Inhibitors of protein kinase C (PKC) also sensitize K562 cells to complement lysis, implicating PKC-mediated signaling in cell resistance to complement. Neutralization of the CD55 and CD59 but not of CD46 regulatory activity with specific antibodies significantly increases complement-mediated K562 cell lysis. Treatment of K562 cells with a mixture of inhibitory reagents results in a significant additive enhancing effect on complement-mediated lysis of K562. In conclusion, K562 cells resist a complement attack by concomitantly using multiple molecular evasion strategies. Future attempts in antibody-based tumor therapy should include strategies to interfere with those resistance mechanisms.     

Loss of CD55 is associated with aggressive breast tumors.

PURPOSE: CD55 is a complement regulatory protein expressed by cells to protect them from bystander attack by complement. CD55 is overexpressed on some tumor cell lines, and in colorectal carcinomas, it has been shown to be an indicator of poor prognostic. EXPERIMENTAL DESIGN: A large set of samples (480) from patients with primary operable breast cancer followed for 4-192 months were included in the present study. The prognostic significance of CD55 was then investigated in these tumors using an anti-CD55 monoclonal antibody (RM1) that we raised against a synthetic peptide and a standard immunohistochemistry method. RESULTS: Ninety-five percent of the breast carcinomas expressed CD55 (RM1) with intensity ranging from weak (51%) to strong (6%). High expression of CD55 was significantly associated with low-grade (grades 1 or 2; P = 0.001), lymph node negativity (P = 0.031), and good prognosis tumors (Nottingham Prognostic Index < 3.4; P < 0.001). Survival analysis showed CD55 overexpression was associated with a more favorable outcome and loss of CD55 being associated with poor survival (P = 0.001). Intensity of CD55 expression was significantly correlated (P = 0.002) with intensity of CD59 expression (as shown in a previous study) in these series of patients. CONCLUSIONS: In conclusion, we found that loss of both CD55 and CD59 in breast carcinomas is associated with a worse prognosis.