髓源抑制细胞作用机制及其在肺癌免疫治疗中作用的研究进展

摘 要：髓源抑制细胞(MDSCs)是肿瘤免疫微环境中主要的免疫抑制细胞,能通过多种机制发挥免疫应答并参与肺癌的发生发展,其在肺癌免疫治疗的重要性也日益显现,是近年来研究的热点。全文就近年来髓源抑制细胞MDSCs在肺癌中的研究进展作一概述。     

髓源性抑制细胞在肺癌中的研究进展

髓源性抑制细胞(Myeloid-derived suppressor cells,MDSCs)是一群来自骨髓不成熟的异质性细胞,表型及成分复杂,在肿瘤微环境中发挥免疫抑制功能,并主要抑制T细胞免疫应答.在肺癌的发生、发展过程中,多种异常表达的细胞因子促进MDSCs增殖与激活,MDSCs活化后参与形成抑制性肿瘤免疫微环境,从而促进肿瘤细胞生长.监测MDSCs的数量与功能变化对评估肺癌的预后有重要意义.一系列针对MDSCs的干预措施在肺癌治疗中获得了重大进展,也为肺部原发及转移瘤的预防带来了希望.     

髓源性抑制细胞联合免疫检查点抑制剂抗肿瘤治疗的研究进展CSCD

免疫检查点抑制剂(ICI)可通过恢复T细胞对肿瘤细胞的识别和损伤功能来增强原有的抗肿瘤免疫应答。ICI已被批准用于黑色素瘤、非小细胞肺癌(NSCLC)和肾细胞癌等多种肿瘤的治疗。然而,许多患者对免疫治疗没有反应。其中部分原因是由髓源性抑制细胞(MDSCs)介导的。这种异质的未成熟骨髓细胞群可以强烈抑制T细胞和NK细胞的抗肿瘤活性并刺激调节性T细胞(Treg)产生免疫抑制,导致肿瘤进展。MDSCs可以促进患者对免疫检查点抑制的耐药。越来越多的证据表明MDSCs在肿瘤患者中的比例和免疫抑制功能可用于治疗反应的预测。本综述重点介绍了MDSCs在免疫检查点抑制中的作用,并提供了MDSCs与ICI靶向联合治疗的策略,以提高后者在肿瘤治疗中的疗效。     

靶向髓系抑制性细胞的药物在肿瘤治疗中的研究进展

髓系抑制性细胞(myeloid-derived suppressor cells,MDSCs)是机体在肿瘤等病理情况下髓系细胞分化发育受阻而形成的一群未成熟的髓系细胞。肿瘤微环境中的MDSCs具有较强的免疫抑制功能,并与肿瘤的发展密切相关,寻找以MDSCs为靶点的药物在肿瘤治疗中具有良好的应用前景。近年来,许多研究发现多种药物通过促进MDSCs分化、或抑制MDSCs扩增、或诱导MDSCs凋亡或减弱MDSCs的免疫抑制功能等方式抑制肿瘤的进展,这些研究为肿瘤的临床治疗提供了新策略。     

糖酵解调控肿瘤中髓系来源抑制细胞的研究进展

髓系来源的抑制细胞（myeloid-derived suppressor cells,MDSCs）是一种骨髓来源的具有异质性及免疫抑制活性的不成熟细胞,常在如炎症、感染及肿瘤等病理情况下由正常骨髓前体细胞增殖分化形成,在肿瘤免疫方面起到重要的作用。而在肿瘤微环境中,有氧糖酵解是其主要糖代谢方式,糖代谢过程的重编程将增强MDSCs的免疫抑制活性,从而抑制效应T细胞的增殖与功能。现有的研究主要涉及腺苷酸活化蛋白激酶（AMP-activated protein kinase,AMPK）,其作为上游调控因子,通过多条信号通路调控下游基因,实现对MDSCs糖代谢的调控。本文将对糖酵解相关信号通路及其对MDSCs功能的影响进行综述。      

髓源性抑制细胞在肿瘤发生发展中的作用

髓源性抑制细胞(myeloid-derived suppressor cells,MDSCs)是一组异质细胞,在肿瘤相关免疫抑制中起关键作用.MDSCs通过免疫抑制作用,使肿瘤逃避免疫监控.肿瘤组织中MDSCs的浸润与患者预后不良及治疗的抵抗密切相关.MDSCs在转移中发挥重要作用,但MDSCs在远处器官建立转移前微环...     

髓源性抑制细胞在构筑转移前微环境促肿瘤转移中的作用

肿瘤细胞持续存活是肿瘤转移过程中的主要限速环节.与肿瘤微环境类似,转移前器官的局部微环境(转移前微环境)为肿瘤细胞的存活提供了适宜的环境,是肿瘤细胞在远端器官持续存活、增殖的重要条件.髓源性抑制细胞(myeloid-derived suppressor cells,MDSCs)是这一环境中的关键成分,其构筑的促增殖、炎症、免疫抑制及血管重塑的转移前微环境在肿瘤细胞的种殖、转移灶的形成过程中具有重要作用,是抗肿瘤转移治疗的潜在靶点.该研究主要介绍MDSCs构筑转移前微环境的机制及相关信号通路,为干预转移前微环境的抗肿瘤转移研究提供参考.     

MDSCs与肿瘤免疫逃逸

髓源抑制性细胞(myeloidderived suppressor cells, MDSCs)是一群异质性细胞,来源于骨髓祖细胞和未成熟髓细胞(immature myeloid cells, IMCs),是树突状细胞（dendritic cells, DCs）、巨噬细胞和（或）粒细胞的前体。在荷瘤小鼠的血液、脾脏和肿瘤组织及肿瘤患者的外周血和肿瘤组织存在大量MDSCs的扩增。MDSCs可以通过多种途径抑制机体的获得性和天然抗肿瘤免疫,使肿瘤细胞逃避机体的免疫监视和攻击,促进肿瘤发展。MDSCs首先从骨髓募集到外周,并在外周被激活后才能发挥抗肿瘤免疫抑制功能,肿瘤来源的慢性炎症相关的一系列因子在介导MDSCs的募集和活化中起关键作用。当前靶向MDSCs的抗肿瘤治疗取得了一定的进展,但MDSCs从发现到现在仅仅经历了10年左右的时间,该领域中许多的未知尚需要大量的基础和临床研究来阐明。本文主要介绍MDSCs的特征及其亚群、MDSCs的募集和活化、MDSCs介导免疫逃逸的机制及当前靶向MDSCs的抗肿瘤治疗策略,以期为从事该领域的研究工作者提供参考。     

IgA的肿瘤免疫抑制作用及其临床意义的研究进展

免疫球蛋白A(IgA)是最常见抗体之一,并在黏膜表面提供第一道免疫保护。IgA⁺B细胞是IgA产生的主要来源细胞。近年来的研究表明,IgA在肿瘤发生发展中呈现双向作用,在不同的肿瘤类型及免疫微环境中发挥不同的作用,尤其是IgA⁺B细胞和IgA的促肿瘤和免疫抑制作用成为目前关注的热点及研究的难点。肿瘤微环境(TME)中IgA⁺B细胞可通过分泌免疫抑制因子,如IL-10、TGF-β、PD-L1、FASL、IL-35和Tim1发挥免疫抑制作用。免疫抑制性IgA在多种肿瘤组织中高表达,并与恶性肿瘤预后差密切相关。本文总结了IgA⁺B细胞和IgA的免疫抑制和促肿瘤作用及其机制,讨论了肿瘤免疫抑制微环境中细胞因子和代谢产物等在调控IgA类转换重组(CSR)中所起的作用,以及IgA免疫抑制作用的临床意义,为肿瘤免疫治疗提供新的思路和治疗策略。     

调节性T细胞参与胰腺癌免疫微环境重塑的基础与转化研究进展

调节性T细胞（regulatory T cells/Treg cells）是发挥负性免疫调节功能的一类CD4+T细胞,主要通过抑制多种效应性T细胞的活性和功能,维持机体获得性免疫系统的平衡,防止自身免疫性疾病的发生。Treg细胞也是免疫抑制性肿瘤微环境的主要组成成分,其在肿瘤局部微环境中,对抗肿瘤免疫应答过程,发挥免疫抑制作用,并协助肿瘤细胞参与免疫逃逸,进而影响肿瘤的恶性演进过程。本文对Treg细胞在胰腺癌免疫微环境重塑过程中发挥功能的机制及其临床转化研究进展进行综述,旨在加深对胰腺癌免疫抑制微环境的认识,为胰腺癌的免疫调节治疗提供新思路。      

髓源抑制性细胞的功能及其逆转策略

髓源抑制性细胞（myeloid-derived suppressor cell,MDSC）是在骨髓中产生的一群具有高度异质性的免疫抑制细胞, 在 肿瘤等病理状态下大量聚集,是促进肿瘤进展、降低患者对传统治疗反应性的关键因素。近年来,免疫检查点阻断剂和基因工程 T细胞过继回输治疗延长了许多晚期恶性肿瘤患者的生存期,但上述免疫疗法在肺癌、结直肠癌等实体瘤中有效率仅为 15%~40%,这与实体瘤免疫抑制微环境密切相关。MDSC在肿瘤微环境中聚集,通过抑制T细胞或NK细胞增殖及功能减弱宿主 抗肿瘤免疫反应,是患者对免疫治疗耐受的关键机制。因此,明确MDSC聚集及功能特征是探索提高免疫治疗效果的重要研究 方向。本文将系统阐述MDSC的产生、聚集及其免疫抑制功能的调控机制,概述目前靶向MDSC治疗的最新研究进展。     

S-1 eliminates MDSCs and enhances the efficacy of PD-1 blockade via regulation of tumor-derived Bv8 and S100A8 in thoracic tumor

Myeloid-derived suppressor cells (MDSCs) have been known to play a pivotal role in the induction of immune tolerance, which limits the benefits of immune checkpoint inhibitors (ICIs). Recent studies revealed that several chemotherapeutic agents decreased tumor-infiltrating MDSCs. Therefore, combination therapy with cytotoxic chemotherapeutic agents and ICIs was approved for first-line treatment for lung cancer. However, the impact of chemotherapeutic agents on MDSCs and an optimal partner of ICIs has not been fully investigated in thoracic tumors, including lung cancer and malignant pleural mesothelioma. In the present study, we found that treatment with 5-FU and its oral formulation, S-1, suppressed tumor progression and inhibited the accumulation of MDSCs in thoracic tumor-bearing mice. Tumor-infiltrating T cells and dendritic cells were significantly expanded in S-1-treated mice. 5-FU suppressed the ability of tumor cells to recruit MDSCs, while it did not suppress the survival and differentiation of mouse MDSCs in vitro. We also revealed that 5-FU or S-1 significantly downregulated the expression of tumor-derived Bv8 and S100A8. The knockdown of Bv8 or S100A8 in tumor cells suppressed tumor growth and MDSC recruitment in vivo. Furthermore, in comparison with pemetrexed, administration of S-1 improved the synergistic therapeutic efficacy of anti-PD-1 antibodies with or without carboplatin. Our findings revealed a novel mechanism wherein S-1 primed a favorable tumor microenvironment to provide the rationale for combination therapy with S-1 and ICIs as the optimal therapy for thoracic cancer.     

Targeting myeloid-derived suppressor cells for cancer therapy

The emergence and clinical application of immunotherapy is considered a promising breakthrough in cancer treatment. According to the literature, immune checkpoint blockade (ICB) has achieved positive clinical responses in different cancer types, although its clinical efficacy remains limited in some patients. The main obstacle to inducing effective antitumor immune responses with ICB is the development of an immunosuppressive tumor microenvironment. Myeloid-derived suppressor cells (MDSCs), as major immune cells that mediate tumor immunosuppression, are intimately involved in regulating the resistance of cancer patients to ICB therapy and to clinical cancer staging and prognosis. Therefore, a combined treatment strategy using MDSC inhibitors and ICB has been proposed and continually improved. This article discusses the immunosuppressive mechanism, clinical significance, and visualization methods of MDSCs. More importantly, it describes current research progress on compounds targeting MDSCs to enhance the antitumor efficacy of ICB.     

Myeloid-derived suppressor cells: Roles in the tumor microenvironment and tumor radiotherapy

Cancer progression is closely related to the tumor microenvironment in which the tumor exists, including surrounding blood vessels, immune cells, fibroblasts, bone marrow-derived inflammatory cells, signaling molecules and the extracellular matrix. Tumors can influence the microenvironment by releasing extracellular signals, promoting tumor angiogenesis and inducing peripheral immune tolerance, while the immune cells in the microenvironment can impact the growth and evolution of cancerous cells. One of major cell components in the tumor microenvironment is myeloid-derived suppressor cells (MDSCs), which promote tumor growth and metastasis directly or indirectly by recognizing other immune cells, producing cytokines and exerting their immunosuppression functions. MDSCs have emerged as major regulators of immune responses in cancer and key targets for treating cancer. There are many limitations and side-effect in approaches of conventional cancer therapy, including radiotherapy. It has grown up to be a burgeoning field that a combination of radiotherapy and immunotherapy applied to cancer therapy. Therefore, it is fundamental to explore the immune mechanism in the process of cancer treatment. Here, we reviewed the recent progress of MDSCs in roles of the tumor microenvironment and tumor radiotherapy.     

The immunobiology of myeloid-derived suppressor cells in cancer

The tumor microenvironment is a complex and heterogeneous milieu in which multiple interactions occur between tumor and host cells. Immunosuppressive cells which are present in this microenvironment, such as regulatory T (Treg) cells and myeloid-derived suppressor cells (MDSCs), play an important role in tumor progression, via down-regulation of antitumor responses. MDSCs represent a heterogeneous group of cells originated from the myeloid lineage that are in the immature state. These cells markedly accumulate under pathologic conditions, such as cancer, infection, and inflammation, and use various mechanisms to inhibit both adaptive and innate immune responses. These immunosuppressive mechanisms include deprivation of T cells from essential amino acids, induction of oxidative stress, interference with viability and trafficking of T cells, induction of immunosuppressive cells, and finally polarizing immunity toward a tumor-promoting type 2 phenotype. In addition to suppression of antitumor immune responses, MDSCs can also enhance the tumor metastasis and angiogenesis. Previous studies have shown that increased frequency of MDSCs is related to the tumor progression. Moreover, various drugs that directly target these cells or reverse their suppressive activity can improve antitumor immune responses as well as increase the efficacy of immunotherapeutic intervention. In this review, we will first discuss on the immunobiology of MDSCs in an attempt to find the role of these cells in tumor progression and then discuss about therapeutic approaches to target these cells.     

手术切除荷瘤淋巴结后小鼠肺组织内CD45+、CD68+、CD163+和CD11b+免疫细胞表达的变化

目的:探讨手术切除荷瘤淋巴结对小鼠远隔脏器肺组织内免疫细胞表达的影响。方法:将小鼠B16F10黑色素瘤细胞接种至小鼠髂下淋巴结（SiLN）,15天后手术切除荷瘤淋巴结,所有小鼠分为手术切除SiLN组和未切除SiLN组（对照组）。应用HE及Elastic-Masson (EM)胶原纤维染色观察小鼠肺组织的一般形态结构和胶原纤维的变化;免疫组化染色观察肺组织中CD45+、CD68+、CD163+和CD11b+免疫细胞表达变化。结果:与对照组相比,手术切除SiLN组小鼠肺组织炎细胞浸润显著增加;血管周围胶原纤维稀疏;CD45+总免疫细胞、CD68+巨噬细胞、CD163+M2型巨噬细胞和CD11b+髓源性抑制性细胞（myeloid-derived suppressor cells,MDSCs）表达均显著增加（P＜0.05）。结论:手术切除荷瘤淋巴结促进小鼠肺组织内CD163+M2型巨噬细胞、CD11b+ MDSCs的表达增加,可能有利于远隔脏器肺组织内支持肿瘤细胞定植的炎性微环境的形成。     

Myeloid‐derived suppressor cells as effectors of immune suppression in cancer

The tumor microenvironment consists of an immunosuppressive niche created by the complex interactions between cancer cells and surrounding stromal cells. A critical component of this environment are myeloid‐derived suppressor cells (MDSCs), a heterogeneous group of immature myeloid cells arrested at different stages of differentiation and expanded in response to a variety of tumor factors. MDSCs exert diverse effects in modulating the interactions between immune effector cells and the malignant cells. An increased presence of MDSCs is associated with tumor progression, poorer outcomes, and decreased effectiveness of immunotherapeutic strategies. In this article, we will review our current understanding of the mechanisms that underlie MDSC expansion and their immune‐suppressive function. Finally, we review the preclinical studies and clinical trials that have attempted to target MDSCs, in order to improve responses to cancer therapies.     

髓源性抑制细胞和调节性T细胞在感染和肿瘤微环境中的免疫抑制机制

髓源性抑制细胞(MDSC)和调节性T细胞(Treg)是重要的抑制性免疫细胞,在炎症、感染和肿瘤中大量扩增,可通过多种机制抑制机体抗肿瘤免疫,促进肿瘤生长和转移.寻找肿瘤微环境中MDSC、Treg细胞升高的原因及清除方法,已成为肿瘤免疫治疗的研究热点.     

A mutual activation loop between breast cancer cells and myeloid-derived suppressor cells facilitates spontaneous metastasis through IL-6 trans-signaling in a murine model

Introduction

Tumor cell interactions with the microenvironment, especially those of bone-marrow-derived myeloid cells, are important in various aspects of tumor metastasis. Myeloid-derived suppressor cells (MDSCs) have been suggested to constitute tumor-favoring microenvironments. In this study, we elucidated a novel mechanism by which the MDSCs can mediate spontaneous distant metastasis of breast cancer cells.

Methods

Murine breast cancer cells, 4T1 and EMT6, were orthotopically grafted into the mammary fat pads of syngeneic BALB/c mice. CD11b⁺Gr-1⁺ MDSCs in the spleen, liver, lung and primary tumor mass were analyzed. To evaluate the role of MDSCs in the distant metastasis, MDSCs were depleted or reconstituted in tumor-bearing mice. To evaluate whether MDSCs in the metastasizing tumor microenvironment affect breast cancer cell behavior, MDSCs and cancer cells were co-cultivated. To investigate the role of MDSCs in in vivo metastasis, we blocked the interactions between MDSCs and cancer cells.

Results

Using a murine breast cancer cell model, we showed that murine breast cancer cells with high IL-6 expression recruited more MDSCs and that the metastasizing capacity of cancer cells paralleled MDSC recruitment in tumor-bearing mice. Metastasizing, but not non-metastasizing, tumor-derived factors induced MDSCs to increase IL-6 production and full activation of recruited MDSCs occurred in the primary tumor site and metastatic organ in the vicinity of metastasizing cancer cells, but not in lymphoid organs. In addition, tumor-expanded MDSCs expressed Adam-family proteases, which facilitated shedding of IL-6 receptor, thereby contributing to breast cancer cell invasiveness and distant metastasis through IL-6 trans-signaling. The critical role of IL-6 trans-signaling was confirmed in both the afferent and efferent pathways of metastasis.

Conclusion

In this study, we showed that metastasizing cancer cells induced higher MDSCs infiltration and prompted them to secret exaggerated IL-6 as well as soluble IL-6Rα, which, in turn, triggered a persistent increase of pSTAT3 in tumor cells. This potential tumor-MDSC axis involving IL-6 trans-signaling directly affected breast cancer cell aggressiveness, leading to spontaneous metastasis.