肺癌围手术期髓系抑制细胞的变化及对肿瘤生长和血管生成的影响

目的:检测肺癌围手术期外周血髓系抑制细胞(myeloid-derived suppressor cells,MDSCs)的变化,并探讨其对肿瘤生长和肿瘤血管生成的影响。方法:采用FCM和血细胞分析技术检测98例肺癌患者围手术期外周血单个核细胞(peripheral blood mononuclear cells,PBMCs)中CD11b~+CD33~+HLA-DR~-细胞百分比和浓度,蛋白芯片和ELISA检测血清中细胞因子的浓度。将围手术期CD11b~+CD33~+人类白细胞抗原DR(human leukocyte antigen-DR,HLA-DR)~-细胞和人肺腺癌细胞A549接种至裸鼠皮下,观察其对肿瘤生长和肿瘤血管生成的影响。结果:肺癌患者术后PBMCs中CD11b~+CD33~+HLA-DR-细胞百分比和浓度均较术前显著升高(P值均<0.05);外周血清CXC趋化因子配体5(CXC chemokine ligand 5,CXCL5)、单核细胞趋化蛋白1(monocyte chemoattractant protein-1,MCP-1)、巨噬细胞炎性蛋白1α(macrophage infl ammatory protein-1α,MIP-1α)/MIP-1β和MIP-3α等趋化因子以及血管内皮生长因子(vascular endothelial growth factor,VEGF)的浓度均较术前显著升高(P值均<0.05)。裸鼠致瘤能力观察结果显示,术后MDSCs促肿瘤生长和肿瘤血管生成的能力较术前MDSCs显著增强(P值均<0.05)。结论:肺癌患者术后PBMCs中MDSCs较术前增加,且其促肿瘤血管生成和肿瘤生长的作用增强,提示MDSCs可能成为预防肿瘤术后转移的新靶点。     

髓样抑制细胞在肿瘤生物学中作用的研究进展

髓样抑制细胞(myeloid-derived suppressor cells,MDSCs)是存在于荷瘤小鼠及肿瘤患者体内、具有免疫抑制功能的细胞群。它由髓系来源的未分化成熟的具有异质性的细胞组成,其中包括树突状细胞、巨噬细胞和粒细胞等。肿瘤细胞分泌的各种因子能诱导MDSCs的产生、运动及活化。荷瘤小鼠来源的MDSCs主要表达CD11b+Gr1+,而肿瘤患者来源的MDSCs主要表达CD11b+CD14-。在荷瘤小鼠骨髓、脾脏和外周血及肿瘤患者的外周血中MDSCs水平升高。MDSCs通过抑制机体免疫功能和促进新生血管生成等机制参与肿瘤的生长及向远处转移。抑制体内MDSCs的功能和降低其数量有助于恢复机体识别、杀伤肿瘤细胞的能力,并提高药物疗效。本文对MDSCs在肿瘤领域的最新研究进展进行综述。     

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。     

三氧化二砷负向调控MDSC的肿瘤免疫抑制功能

目的:研究三氧化二砷(arsenic trioxide,As2O3)是否通过抑制髓系来源抑制性细胞(myeloid-derived suppressor cells,MDSCs)负向调控MDSCs诱导的肿瘤免疫耐受作用.方法:C57BL/6小鼠皮下注射黑素瘤B16细胞和肝癌H22细胞构建移植瘤模型,As2O3处理,观察移植瘤生长情况,流式细胞术检测荷瘤小鼠脾脏内MDSCs和其他免疫细胞的免疫表型,流式细胞术检测2 μmol/L As2O3对B16模型小鼠来源的MDSCs分化的影响.取B16模型小鼠随机分为As2O3处理及对照组,混合淋巴细胞反应检测MDSCs对T细胞免疫抑制活性的改变,ELISA检测B16模型小鼠血清及MDSCs培养上清中TNF-α、IL-10的水平.结果:As2O3抑制B16和H22模型鼠的肿瘤生长,延长B16模型小鼠的生存期,并可显著下调小鼠脾脏内MDSCs的比例.体外经2 μmol/L As2O3处理5d后,B16模型小鼠来源的MDSCs中成熟DCs(CD11c+ CD40+)的比例较对照组显著升高[(27.38±4.57)％ vs (17.44±4.51)％,P=0.0078];As2O3组来源的MDSCs对T细胞的免疫抑制活性明显低于对照组(P =0.016);As2O3组小鼠血清及MDSCs培养上清中TNF-α(F=5.78,P=0.014)和IL-10(F=17.83,P=0.045)的含量均较对照组显著降低.结论:As2O3可通过诱导MDSCs向成熟表型分化、下调其免疫抑制活性等,负调控MDSCs的肿瘤免疫抑制功能.     

TGFβ信号通路的阻断导致乳腺癌细胞募集Gr-1+CD11b+髓样免疫抑制细胞促进肿瘤的转移

TGFβ信号通路的异常对于肿瘤的发生发展有着密切的关系。在肿瘤发生早期，TGF6发挥肿瘤抑制因子的作用，TGFβ通路的失活通常会导致肿瘤的发生。然而随着肿瘤的不断发展，TGFβ的作用开始变得复杂化。Gr-1＋CD11b＋髓系来源的髓样细胞又称为髓样免疫抑制细胞（MISCs）或髓系来源的抑制细胞（MDSCs）是近年来免疫学研究的热点之一。在小鼠体内它们同时表达巨噬细胞系的髓样细胞表面标识CD11b和粒细胞表面标识Gr-1，因此得名。目前研究表明，该群细胞发挥着免疫抑制作用，对于肿瘤的免疫逃逸起关键作用。     

髓系来源的抑制性细胞在小鼠H22原位种植性肝癌中的表达及其意义

目的:比较小鼠H22原位种植性肝癌模型中髓系来源的抑制性细胞（MDSCs）和调节性T细胞（Tregs）的表达，确定主要的免疫抑制性细胞。并探讨主要免疫抑制性细胞在小鼠H22原位种植性肝癌模型中的意义。方法:建立小鼠H22原位种植性肝癌模型，用流式细胞术的方法比较外周血、脾脏、肿瘤组织中MDSCs、Tregs的比例。分析MDSCs与CD4+T细胞、CD8+T细胞、NK细胞、NKT细胞的相关性。通过脾脏切除的方法下调MDSCs的表达，观察对肿瘤存活的影响。结果:MDSCs的比例无论在外周血、脾脏还是肿瘤组织中都显著高于Tregs。MDSCs的比例与CD4+T细胞、CD8+T细胞、NK细胞、NKT细胞呈负相关。下调MDSCs的比例可以显著延长小鼠存活期。结论:小鼠H22原位种植性肝癌中主要的免疫抑制性细胞是MDSCs。MDSCs的高表达预示着不良的小鼠存活期。     

抗Gr-1抗体降低肺癌小鼠髓源性抑制细胞对CD8+T细胞数量和肿瘤生长的影响

目的探讨通过抗Gr-1抗体降低Lewis肺癌小鼠髓源性抑制细胞(MDSC)对肿瘤生长及对外周血、脾脏、肿瘤组织中CD8+ T细胞数量的影响。方法构建小鼠肺癌Lewis细胞荷瘤小鼠模型。每48 h腹腔注射抗Gr-1抗体降低MDSC(观察组), 以注射等量0.7% NaCl溶液的模型小鼠为对照组, 持续3周。接瘤第7、14、21天分别处死3只小鼠, 应用流式细胞仪动态监测各时间点小鼠外周血、脾脏、肿瘤组织中MDSC、CD8+ T细胞的比例;接瘤7 d后, 定时测量小鼠皮下肿瘤的长径、短径, 监测两组肿瘤大小。结果两组肿瘤体积均随时间延长而增长, 其中观察组上升趋势相对缓慢, 第20天观察组肿瘤体积较对照组小[(1 978±315)mm3比(1 356±432)mm3, P=0.001]。接瘤后第7、14、21天, 观察组小鼠外周血、脾脏、肿瘤组织中MDSC和CD8+ T细胞比例均低于对照组。两组小鼠外周血中MDSC比例随时间推移均呈上升趋势, 其中观察组小鼠MDSC比例上升趋势较对照组缓慢;两组外周血中CD8+ T细胞比例在第7天至第14天均呈现上升趋势, 且观察组上升趋势更明显, 第14...     

水飞蓟素通过调控骨髓来源的抑制性细胞抗肺癌机制的实验研究

目的:研究水飞蓟素通过调控骨髓来源的抑制性细胞（MDSC）的抗肺癌机制。方法:我们在C57/BL6小鼠上构建了路易斯（Lewis）肺癌细胞转移瘤模型，灌胃给予不同浓度(25、50 mg/kg,每天一次)的水飞蓟素。测量小鼠肿瘤体积及体重变化。用免疫组化方法检测Lewis肺癌细胞肿瘤增殖相关指标增殖细胞核抗原（PCNA）的表达。通过TUNEL染色检测肺癌细胞的凋亡情况。通过免疫组化检测组织中CD8+ T细胞浸润及功能。通过流式细胞术检测CD11b+Gr-1+的MDSC百分比。通过Q-PCR检测肿瘤组织中Arg-1、iNOS2及MMP9的表达。结果:25和50 mg/kg的水飞蓟素剂量依赖地抑制肿瘤生长，诱导肿瘤细胞凋亡。水飞蓟素增加了CD8+ T细胞浸润；减少了肿瘤组织中MDSC的比例，肿瘤组织中Arg-1、iNOS2 及MMP9（MDSC功能相关） mRNA表达的减少也证实了MDSC功能的减弱。结论:水飞蓟素抑制了MDSC，促进CD8+ T细胞浸润及功能，抑制模型中肿瘤生长，为水飞蓟素治疗肺癌提供了依据。     

乳腺癌患者髓系来源抑制性细胞的鉴定与免疫作用研究

目的:探讨乳腺癌患者体内一群髓系来源抑制性细胞(MDSCs)的表型特点及它对淋巴细胞的抑制作用.方法:收集20例乳腺癌患者外周血及肿瘤组织,10例体检正常健康者外周血,通过流式和免疫组织化学染色技术检测MDSCs的表型特点及比例.采用免疫磁珠技术分选乳腺癌患者肿瘤中的MDSCs,通过瑞氏染色观察细胞形态,分别利用MTT法、流式细胞术和ELISA法检测其对自体淋巴细胞增殖、凋亡和细胞因子分泌的影响.结果:流式细胞仪检测结果显示乳腺癌患者肿瘤组织及外周血中有一群具有髓系前体细胞形态的MDSCs,表面标志为CD45+ CD13+CD33+CD14-CD15-.实验结果显示肿瘤组织来源的MDSCs显著抑制自体淋巴细胞增殖,促进其调亡,并显著抑制其分泌IFN-γ,促进TGF-β、IL-10释放.结论:乳腺癌患者肿瘤组织中存在一群具有独特表型特点的MDSCs,不仅抑制自体淋巴细胞增殖和因子分泌,同时促进细胞凋亡.     

乳腺癌髓系来源抑制细胞中IDO表达与调节性T细胞相关性及其临床意义的研究

  目的  研究不同期别乳腺癌组织中CD33+髓系来源抑制细胞(MDSCs)和Foxp3+调节性T细胞(Tregs)的分布情况, 探讨MDSCs中吲哚胺2, 3-双加氧酶(IDO)表达与Tregs分布关系及其临床意义。   方法  收集天津医科大学附属肿瘤医院2005年1月至2007年1月手术患者的乳腺癌石蜡切片50例, 采用免疫组织化学单染方法对肿瘤局部CD33+MDSCs和Foxp3+Tregs分布和比例进行检测; 采用免疫组织化学双染方法检测肿瘤原位浸润MDSCs中IDO的表达情况; 分析MDSCs中IDO表达与Tregs分布、比例及其他临床病理资料之间的相关性。   结果  Foxp3+Tregs和CD33+MDSCs细胞在乳腺癌组织中呈散在性分布。MDSCs中IDO表达水平与腋窝淋巴结转移密切相关(P < 0.05)。Foxp3+Tregs高表达组中MDSCs中IDO表达水平显著高于Foxp3+Tregs低表达或不表达组(P < 0.05)。   结论  MDSCs中IDO过表达可能有利于Tregs的募集和乳腺癌的转移。      

The influence of myeloid‐derived suppressor cells on angiogenesis and tumor growth after cancer surgery

While myeloid‐derived suppressor cells (MDSCs) have been reported to participate in the promotion of angiogenesis and tumor growth, little is known about their presence and function during perioperative period. Here, we demonstrated that human MDSCs expressing CD11b⁺, CD33⁺ and HLA‐DR^– significantly increased in lung cancer patients after thoracotomy. CD11b⁺ CD33⁺ HLA‐DR^– MDSCs isolated 24 hr after surgery from lung cancer patients were more efficient in promoting angiogenesis and tumor growth than MDSCs isolated before surgical operation in allograft tumor model. In addition, CD11b⁺ CD33⁺ HLA‐DR^– MDSCs produced high levels of MMP‐9. Using an experimental lung metastasis mouse model, we demonstrated that the numbers of metastases on lung surface and Gr‐1⁺ CD11b⁺ MDSCs at postoperative period were enhanced in proportion to the degree of surgical manipulation. We also examined that syngeneic bone marrow mesenchymal stem cells (BMSCs) significantly inhibited the induction and proliferation of Gr‐1⁺ CD11b⁺ MDSCs and further prevented lung metastasis formation in the mice undergoing laparotomy. Taken together, our results suggest that postoperatively induced MDSCs were qualified with potent proangiogenic and tumor‐promotive ability and this cell population should be considered as a target for preventing postoperative tumor metastasis.     

Abrogation of TGF beta signaling in mammary carcinomas recruits Gr-1+CD11b+ myeloid cells that promote metastasis

Aberrant TGFbeta signaling is common in human cancers and contributes to tumor metastasis. Here, we demonstrate that Gr-1+CD11b+ myeloid cells are recruited into mammary carcinomas with type II TGF beta receptor gene (Tgfbr2) deletion and directly promote tumor metastasis. Gr-1+CD11b+ cells infiltrate into the invasive front of tumor tissues and facilitate tumor cell invasion and metastasis through a process involving metalloproteinase activity. This infiltration of Gr-1+CD11b+ cells also results in increased abundance of TGF beta 1 in tumors with Tgfbr2 deletion. The recruitment of Gr-1+CD11b+ cells into tumors with Tgfbr2 deletion involves two chemokine receptor axes, the SDF-1/CXCR4 and CXCL5/CXCR2 axes. Together, these data indicate that Gr-1+CD11b+ cells contribute to TGFbeta-mediated metastasis through enhancing tumor cell invasion and metastasis.     

Gr-1+CD11b+ cells are responsible for tumor promoting effect of TGF-β in breast cancer progression

One great challenge in our understanding of TGF-β cancer biology and the successful application of TGF-β-targeted therapy is that TGF-β works as both a tumor suppressor and a tumor promoter. The underlying mechanisms for its functional change remain to be elucidated. Using 4T1 mammary tumor model that shares many characteristics with human breast cancer, particularly its ability to spontaneously metastasize to the lungs, we demonstrate that Gr-1+CD11b+ cells or myeloid derived suppressor cells are important mediators in TGF-β regulation of mammary tumor progression. Depletion of Gr-1+CD11b+ cells diminished the antitumor effect of TGF-β neutralization. Two mechanisms were involved: first, treatment with TGF-β neutralization antibody (1D11) significantly decreased the number of Gr-1+CD11b+ cells in tumor tissues and premetastatic lung. This is mediated through increased Gr-1+CD11b+ cell apoptosis. In addition, 1D11 treatment significantly decreased the expression of Th2 cytokines and Arginase 1. Interestingly, the number and property of Gr-1+CD11b+ cells in peripheral blood/draining lymph nodes correlated with tumor size and metastases in response to 1D11 treatment. Our data suggest that the efficacy of TGF-β neutralization depends on the presence of Gr-1+CD11b+ cells, and these cells could be good biomarkers for TGF-β-targeted therapy.     

CD80 in immune suppression by mouse ovarian carcinoma-associated Gr-1+CD11b+ myeloid cells

An elevated number of Gr-1+CD11b+ myeloid cells has been described in mice bearing transplantable tumors, and has been associated with immune suppression. We examined the role of such myeloid suppressor cells in mice bearing the spontaneously transformed syngeneic mouse ovarian surface epithelial cell line, 1D8. We observed high levels of CD80 expression by Gr-1+CD11b+ cells from spleen, ascites, and tumor tissue of mice bearing 1D8 ovarian carcinoma, whereas CD40 and CD86 were absent. CD80 expression was not detected on Gr-1+CD11b+ cells from na?ve mice. However, the expression of CD80 by Gr-1+CD11b+ cells from na?ve mice was promoted by coculture with 1D8 cells. Because irradiated 1D8 cells, but not 1D8-conditioned medium, up-regulate CD80 expression by Gr-1+CD11b+ cells, this phenomenon likely requires direct interaction. Gr-1+CD11b+ cells derived from 1D8 tumor-bearing mice provided significant suppression of antigen-specific immune responses, but Gr-1+CD11b+ cells from na?ve mice did not. Both short interfering RNA-mediated knockdown and genetic knockout of CD80 expression by Gr-1+CD11b+ cells of 1D8 tumor-bearing mice alleviated the suppression of antigen-specific immune responses. Suppression via CD80 on Gr-1+CD11b+ myeloid cells was mediated by CD4+CD25+ T regulatory cells and required CD152. CD80 knockout or antibody blockade of either CD80 or CD152 retarded the growth of 1D8 tumor in mice, suggesting that expression of CD80 on Gr-1+CD11b+ myeloid cells triggered by 1D8 ovarian carcinoma suppresses antigen-specific immunity via CD152 signaling and CD4+CD25+ T regulatory cells. Thus, CD80-dependent responses to myeloid suppressor cells may contribute to tumor tolerance and the progression of ovarian carcinoma.     

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.     

Adenoviral transduction of MRP-1/CD9 and KAI1/CD82 inhibits lymph node metastasis in orthotopic lung cancer model

Conventional therapies still remain less effective for metastasis of lung cancer, thus leading to a poor prognosis for this disorder. Although the processes involved in metastasis have not yet been clearly elucidated, our previous studies have shown that higher expression levels of MRP-1/CD9 and KAI1/CD82 in cancer cells are significantly correlated with less metastatic potency. To determine whether the gene transfer of these tetraspanins into lung tumor cells may be a useful strategy to regulate metastasis, we adopted an orthotopic lung cancer model produced by the intrapulmonary implantation of Lewis lung carcinoma (LLC) cells and evaluated the metastatic growth in the mediastinal lymph nodes using two different methods of gene delivery as follows: (a) the implantation of LLC cells preinfected with adenovirus encoding either MRP-1/CD9 cDNA, KAI1/CD82 cDNA, or LacZ gene into the mouse lung and (b) the intratracheal administration of these adenoviruses into the mice orthotopically preimplanted with LLC cells. In both cases, we found that the delivery of either MRP-1/CD9 or KAI1/CD82 cDNA dramatically reduced the metastases to the mediastinal lymph nodes in comparison with those of LacZ gene delivery, without affecting the primary tumor growth at the implanted site. These results reemphasize the important role of MRP-1/CD9 and KAI1/CD82 in the suppression of the metastatic process and also show the feasibility of gene therapy when using these tetraspanins for lung cancer to prevent metastasis to the regional lymph nodes. This strategy may therefore be clinically applicable as a prophylactic treatment to suppress the occurrence of lymph node metastasis.     

Core Needle Biopsy of Breast Cancer Tumors Increases Distant Metastases in a Mouse Model

INTRODUCTION: Incisional biopsies, including the diagnostic core needle biopsy (CNB), routinely performed before surgical excision of breast cancer tumors are hypothesized to increase the risk of metastatic disease. In this study, we experimentally determined whether CNB of breast cancer tumors results in increased distant metastases and examine important resultant changes in the primary tumor and tumor microenvironment associated with this outcome. METHOD: To evaluate the effect of CNB on metastasis development, we implanted murine mammary 4T1 tumor cells in BALB/c mice and performed CNB on palpable tumors in half the mice. Subsequently, emulating the human scenario, all mice underwent complete tumor excision and were allowed to recover, with attendant metastasis development. Tumor growth, lung metastasis, circulating tumor cell (CTC) levels, variation in gene expression, composition of the tumor microenvironment, and changes in immunologic markers were compared in biopsied and non-biopsied mice. RESULTS: Mice with biopsied tumors developed significantly more lung metastases compared to non-biopsied mice. Tumors from biopsied mice contained a higher frequency of myeloid-derived suppressor cells (MDSCs) accompanied by reduced CD4 + T cells, CD8 + T cells, and macrophages, suggesting biopsy-mediated development of an increasingly immunosuppressive tumor microenvironment. We also observed a CNB-dependent up-regulation in the expression of SOX4, Ezh2, and other key epithelial-mesenchymal transition (EMT) genes, as well as increased CTC levels among the biopsy group. CONCLUSION: CNB creates an immunosuppressive tumor microenvironment, increases EMT, and facilitates release of CTCs, all of which likely contribute to the observed increase in development of distant metastases.Abbreviations: CCAC, Canadian Council on Animal Care; CNB, core needle biopsy; CTCs, circulating tumor cells; EMT, epithelial-mesenchymal transition; H&E, hematoxylin and eosin; MDSCs, myeloid-derived suppressor cells; PGE2, prostaglandin E2     

Myeloid suppressor cells regulate the lung environment--letter

4T1 murine mammary carcinoma cells implanted in syngeneic Balb/c mice are increasingly being used in metastasis research, with some groups using this model to study tumor-induced accumulation of bone marrow-derived cells in metastatic target organs. Bone marrow-derived cells (including CD11b(+)Gr-1(+) myelomonocytic cells) are thought to modify the local lung microenvironment to facilitate subsequent colonization by metastatic tumor cells. While quantification of metastatic 4T1 tumor cells in various tissues can be done using ex vivo colony-forming assays, detection of metastatic 4T1 cells is often facilitated by expressing fluorescent proteins in the tumor cells prior to implantation. We found that Balb/c mice mount a potent immune response against 4T1 cells expressing green fluorescent protein (GFP) that includes the generation of anti-GFP antibodies in the circulation. Importantly, the number of bone marrow-derived CD11b(+)Gr-1(+) cells and metastatic tumor cells that accumulate in the lungs is significantly decreased in mice implanted with 4T1 cells expressing GFP compared with mice bearing wild-type 4T1 tumors. Taken together, our data caution against the use of GFP-expressing tumor cells in the Balb/c mouse strain, particularly for studying the influence of immunomodulatory cells on tumor cell metastasis.     

An expanded myeloid derived suppressor cell population does not play a role in gammaherpesvirus-exacerbated breast cancer metastases

ABSTRACT: BACKGROUND: Mice latently infected with murine gammaherpesvirus 68 (HV-68) and transplanted with 4 T1 breast cancer cells developed exacerbated metastatic lesions when compared to controls. The mechanisms responsible for this viral-exacerbated disease were not clear. The ability of HV-68 infection to induce S100A8 and S100A9 production and to expand a population of CD11b+Gr-1+ cells suggested that increased numbers, or activity, of viral-expanded myeloid derived suppressor cells (MDSCs) might contribute to HV-68-associated metastatic breast cancer in this model. We questioned whether mock or HV-68 infected mice with significant breast cancer might have differences in the number and/or activity of MDSCs. METHODS: Myeloid-derived macrophages and dendritic cells were isolated from normal mice and cultured in vitro with HV-68 to assess S100A8 and S100A9 mRNA and protein expression. In vivo studies were performed using groups of mice that were mock treated or infected with HV-68. After viral latency was established, 4 T1 breast cancer cells were transplanted in mice. When primary breast tumors were present mice were euthanized and cells isolated for phenotyping of myeloid cell populations using FACS, and for ex vivo analysis of suppressor activity. Serum from these animals was also collected to quantify S100A8 and S100A9 levels. RESULTS: In vitro studies demonstrated that direct exposure of myeloid cells to HV-68 did not induce increased expression of S100A8 or S100A9 mRNAs or secreted protein. HV-68 infected mice with metastatic breast cancer disease had no increases in S100A8/A9 levels and no significant increases in the numbers or activation of CD11b+Gr-1+MDSCs when compared to mock treated mice with breast cancer. CONCLUSIONS: Together these studies are consistent with the notion that expanded myeloid derived suppressor cells do not play a role in gammaherpesvirus-exacerbated breast cancer metastases. The mechanisms responsible for HV-68 induced exacerbation of metastatic breast cancer remain unclear.