成纤维细胞激活蛋白alpha与肿瘤免疫抑制的研究进展

成纤维细胞激活蛋白alpha（Fibroblast activation protein-alpha,FAP-alpha）是一种跨膜丝氨酸蛋白酶,高度表达在90 %的上皮性肿瘤的 间质--肿瘤相关成纤维细胞（Tumor association fibroblast,TAF）上。FAPalpha在促进上皮性肿瘤的恶性进展中起着十分重要的作用, 近年来研究发现,FAP琢在肿瘤微环境中发挥免疫抑制的作用。研究FAPalpha在肿瘤免疫抑制中的作用,已成为肿瘤研究的新的热 点。为基于以FAP-alpha为靶标的抗肿瘤免疫治疗提供参考,本文围绕引起肿瘤免疫抑制的因素、FAPalpha与肿瘤免疫抑制的研究进展 以及FAP-alpha在肿瘤的发展进程的作用作一综述。     

成纤维细胞激活蛋白α与肿瘤免疫抑制的研究进展

成纤维细胞激活蛋白α(Fibroblast activation proteinα,FAPα)是一种跨膜丝氨酸蛋白酶,高度表达在90%的上皮性肿瘤的间质--肿瘤相关成纤维细胞(Tumor association fibroblast,TAF)上。FAPα在促进上皮性肿瘤的恶性进展中起着十分重要的作用,近年来研究发现,FAPα在肿瘤微环境中发挥免疫抑制的作用。研究FAPα在肿瘤免疫抑制中的作用,已成为肿瘤研究的新的热点。为基于以FAPα为靶标的抗肿瘤免疫治疗提供参考,本文围绕引起肿瘤免疫抑制的因素、FAPα与肿瘤免疫抑制的研究进展以及FAPα在肿瘤的发展进程的作用作一综述。     

成纤维细胞激活蛋白α与肿瘤发展进程的研究

肿瘤微环境对肿瘤的发生、发展具有重要的意义。选择性表达于肿瘤微环境重要组成部分——肿瘤相关成纤维细胞（carcinoma associated fibroblasts,CAFs）表面的成纤维细胞激活蛋白α（fibroblast activation protein-α,FAPα）广泛参与了肿瘤的生长、侵袭、转移以及肿瘤细胞外基质重建、血管生成、免疫逃逸等过程,从而促进了肿瘤的发展进程。FAPα具有蛋白水解酶活性,并作用于细胞信号通路,但FAPα在肿瘤微环境中发挥功能的具体分子机制还有待进一步研究。由于FAPα的表达具有肿瘤组织特异性,因此,以FAPα作为肿瘤基质标志物,对肿瘤进行病理诊断和免疫治疗将成为新兴的研究靶点。对FAPα的主要生物学性状进行概述,并综述了其对肿瘤细胞的生长、侵袭、转移以及肿瘤细胞外基质重建、血管生成、免疫逃逸等方面的重要影响。     

肿瘤相关成纤维细胞与肿瘤微环境

肿瘤的发展过程与肿瘤微环境密切相关,而肿瘤相关成纤维细胞（CAFs）是上述微环境中最主要的宿主细胞,CAFs是一类不同细胞源性的细胞群,可来源于多种细胞包括静止的成纤维细胞、上皮细胞、内皮细胞和间质干细胞的分化过程。体内和体外生物学实验均证实,成纤维细胞在肿瘤微环境中并不是被动的对肿瘤发展提供支持,而是发挥了至关重要的作用,所以靶向CAFs有望成为肿瘤治疗的新方向,对CAFs相关分子标记物和分子事件的进一步探索将为抗肿瘤的临床治疗提供新的思路。本文将对CAFs的来源以及CAFs对肿瘤发生发展、转移及VEGF耐受等方面的作用做一综述。     

肿瘤相关成纤维细胞与肿瘤微环境

肿瘤的发展过程与肿瘤微环境密切相关,而肿瘤相关成纤维细胞(CAFs)是上述微环境中最主要的宿主细胞,CAFs是一类不同细胞源性的细胞群,可来源于多种细胞包括静止的成纤维细胞、上皮细胞、内皮细胞和间质干细胞的分化过程。体内和体外生物学实验均证实,成纤维细胞在肿瘤微环境中并不是被动的对肿瘤发展提供支持,而是发挥了至关重要的作用,所以靶向CAFs有望成为肿瘤治疗的新方向,对CAFs相关分子标记物和分子事件的进一步探索将为抗肿瘤的临床治疗提供新的思路。本文将对CAFs的来源以及CAFs对肿瘤发生发展、转移及VEGF耐受等方面的作用做一综述。     

肿瘤相关成纤维细胞促进肿瘤侵袭转移的作用机制

肿瘤相关成纤维细胞(cancer-associated fibroblasts,CAFs)是肿瘤微环境中最主要的成分之一,在肿瘤的发生发展中发挥着必不可少的作用。骨髓和脂肪的局部组织固有成纤维细胞及间充质干细胞是CAFs来源的主要前体细胞。大量研究表明,CAFs并不作为单独细胞在肿瘤周围存在,而是和肿瘤细胞相互作用,促进肿瘤的生长与存活并维持其恶性倾向。肿瘤细胞可以影响CAFs前体的招募,并诱导正常成纤维细胞活化为CAFs;同时,CAFs可以分泌多种细胞因子、生长因子和细胞外基质蛋白质,促进肿瘤细胞的增殖、耐药及侵袭转移,从而影响肿瘤的预后。CAFs还参与血管淋巴管的生成、细胞外基质重塑、免疫抑制以及肿瘤细胞上皮间质转化等有利于肿瘤发生发展的外源性途径,为肿瘤细胞提供了一个良好的微环境。大量研究显示,研发靶向CAFs的药物可以中断其与肿瘤细胞之间的联系,从而抑制肿瘤的生长和转移。因此,深入了解CAFs促肿瘤的作用机制将有利于肿瘤治疗新靶点的发现。本文将对CAFs促进肿瘤侵袭转移的作用机制加以综述。     

成纤维细胞激活蛋白α与肿瘤的靶向治疗

成纤维细胞激活蛋白α（FAPα）是肿瘤相关成纤维细胞特异性表达的一种表面抗原,具有二肽基肽酶和胶原酶活性,在肿瘤的生长、浸润、转移中发挥重要作用。故以FAPα作为肿瘤基质标志物的病理诊断、肿瘤基因治疗或免疫治疗将成为可能。本文就近年来对FAPα结构特点、活性作用及在肿瘤诊治中的研究进展进行综述。     

综述: 细胞外基质与肿瘤相关成纤维细胞

肿瘤的发生发展是一个肿瘤细胞与其微环境相互促进,共同演化的动态过程．实体肿瘤的发生发展过程伴随细胞外基质的过量沉积及其组织形式的异常以及成纤维细胞的活化和富集．细胞外基质与肿瘤相关成纤维细胞不仅是实体肿瘤的重要病理特征,同时也是恶性肿瘤发展的重要驱动力量．细胞外基质与肿瘤相关成纤维细胞通过多种机制促进了肿瘤的发生、发展和转移．针对细胞外基质与肿瘤相关成纤维细胞进行肿瘤治疗,可以为肿瘤的临床治疗提供新的思路．     

结缔组织生成和肿瘤

肿瘤的发生并不只是由肿瘤细胞本身恶化引起的,肿瘤基质也发挥了非常重要的作用,肿瘤发生是肿瘤细胞和围绕它的肿瘤基质相互作用的产物。肿瘤细胞可以通过各种途径激活与其相邻的间质,促进成纤维细胞的增生、细胞外基质的沉积、免疫细胞浸润和血管生成,这种现象被称为结缔组织生成。结缔组织生成形成了一个支持肿瘤发展的微环境,通过多种途径促进了肿瘤的发生、发展和转移。针对结缔组织生成进行肿瘤治疗可以为肿瘤的临床治疗提供新的思路。     

结缔组织生成和肿瘤

肿瘤的发生并不只是由肿瘤细胞本身恶化引起的,肿瘤基质也发挥了非常重要的作用,肿瘤发生是肿瘤细胞和围绕它的肿瘤基质相互作用的产物。肿瘤细胞可以通过各种途径激活与其相邻的间质,促进成纤维细胞的增生、细胞外基质的沉积、免疫细胞浸润和血管生成,这种现象被称为结缔组织生成。结缔组织生成形成了一个支持肿瘤发展的微环境,通过多种途径促进了肿瘤的发生、发展和转移。针对结缔组织生成进行肿瘤治疗可以为肿瘤的临床治疗提供新的思路。     

Therapeutic gene modified cell based cancer vaccines

History of cancer immunotherapy lasts for more than 120 years. In 1891 William B. Coley injected bacteria into inoperable cancer (bone sarcoma) and observed tumor shrinkage. He is recognized as the "'"Father of Immunotherapy"'". Cancer immunotherapy is based on the ability of the immune system to recognize cancer cells and to affect their growth and expansion. Beside the fact that, tumor cells are genetically distinct from their normal counterparts, and should be recognized and eliminated by immune system, the tumor associated antigens (TAAs) are often poorly immunogenic due to immunoediting. This process allows tumor to evolve during continuous interactions with the host immune system, and eventually escape from immune surveillance. Furthermore, tumor microenvironment consists of immunosuppressive cells that release immunosuppressive factors including IL-6, IL-10, IDO, TGFβ or VEGF. Interactions between cancer and stroma cells create network of immunosuppressive pathways, while activation of immune defense is inhibited. A key to successful immunotherapy is to overcome the local immunosuppression within tumor microenvironment and activate mechanisms that lead to tumor eradication. There are two clinical approaches of immunotherapy: active and passive. Active immunotherapy involves stimulation of immune response to tumor associated antigens (TAAs), either non-specifically via immunomodulating agents or specifically employing cancer vaccines. This review presents the progress and breakthroughs in design, development and clinical application of selected cell-based tumor vaccines achieved due to the generation and development of gene transfer technologies.     

Cancer Associated Fibroblasts Promote Tumor Growth and Metastasis by Modulating the Tumor Immune Microenvironment in a 4T1 Murine Breast Cancer Model

Background

Local inflammation associated with solid tumors commonly results from factors released by tumor cells and the tumor stroma, and promotes tumor progression. Cancer associated fibroblasts comprise a majority of the cells found in tumor stroma and are appealing targets for cancer therapy. Here, our aim was to determine the efficacy of targeting cancer associated fibroblasts for the treatment of metastatic breast cancer.

Methodology/Principal Findings

We demonstrate that cancer associated fibroblasts are key modulators of immune polarization in the tumor microenvironment of a 4T1 murine model of metastatic breast cancer. Elimination of cancer associated fibroblasts in vivo by a DNA vaccine targeted to fibroblast activation protein results in a shift of the immune microenvironment from a Th2 to Th1 polarization. This shift is characterized by increased protein expression of IL-2 and IL-7, suppressed recruitment of tumor-associated macrophages, myeloid derived suppressor cells, T regulatory cells, and decreased tumor angiogenesis and lymphangiogenesis. Additionally, the vaccine improved anti-metastatic effects of doxorubicin chemotherapy and enhanced suppression of IL-6 and IL-4 protein expression while increasing recruitment of dendritic cells and CD8⁺ T cells. Treatment with the combination therapy also reduced tumor-associated Vegf, Pdgfc, and GM-CSF mRNA and protein expression.

Conclusions/Significance

Our findings demonstrate that cancer associated fibroblasts promote tumor growth and metastasis through their role as key modulators of immune polarization in the tumor microenvironment and are valid targets for therapy of metastatic breast cancer.     

The effects of CA IX catalysis products within tumor microenvironment

Solid tumors are composed of both cancer cells and various types of accessory cells, mainly fibroblasts, that collectively compose the so called tumor-microenvironment. Cancer-associated fibroblasts have been described to actively participate in cancer progression by establishing a cytokine-mediated as well as metabolic crosstalk with cancer cells. In the present paper we show that activated human fibroblasts are able to boost tumor cells proliferation and that this effect is greatly dependent on stromal carbonic anhydrase IX (CA IX) activity. In fact fibroblasts show a strong upregulation of CA IX expression upon activation by cancer cells, while CA IX products, protons and bicarbonate, exert differential effects on cancer cells proliferation. While acidification of extracellular pH, a typical condition of rapidly growing solid tumors, is detrimental for tumor cells proliferation, bicarbonate, through its organication, supplies cancer cells with intermediates useful to sustain their high proliferation rate. Here we propose a new kind of fibroblasts/tumor cells crosstalk within tumor microenvironment, mediated by stromal CA IX products, aimed to favor cancer cells growth, opening new perspectives on CA IX role in tumor microenvironment.     

BRCA1 mutations drive oxidative stress and glycolysis in the tumor microenvironment

Mutations in the BRCA1 tumor suppressor gene are commonly found in hereditary breast cancer. Similarly, downregulation of BRCA1 protein expression is observed in the majority of basal-like breast cancers. Here, we set out to study the effects of BRCA1 mutations on oxidative stress in the tumor microenvironment. To mimic the breast tumor microenvironment, we utilized an in vitro co-culture model of human BRCA1-mutated HCC1937 breast cancer cells and hTERT-immortalized human fibroblasts. Notably, HCC1937 cells induce the generation of hydrogen peroxide in the fibroblast compartment during co-culture, which can be inhibited by genetic complementation with the wild-type BRCA1 gene. Importantly, treatment with powerful antioxidants, such as NAC and Tempol, induces apoptosis in HCC1937 cells, suggesting that microenvironmental oxidative stress supports cancer cell survival. In addition, Tempol treatment increases the apoptotic rates of MDA-MB-231 cells, which have wild-type BRCA1, but share a basal-like breast cancer phenotype with HCC1937 cells. MCT4 is the main exporter of L-lactate out of cells and is a marker for oxidative stress and glycolytic metabolism. Co-culture with HCC1937 cells dramatically induces MCT4 protein expression in fibroblasts, and this can be prevented by either BRCA1 overexpression or by pharmacological treatment with NAC. We next evaluated caveolin-1 (Cav-1) expression in stromal fibroblasts. Loss of Cav-1 is a marker of the cancer-associated fibroblast (CAF) phenotype, which is linked to high stromal glycolysis, and is associated with a poor prognosis in numerous types of human cancers, including breast cancers. Remarkably, HCC1937 cells induce a loss of Cav-1 in adjacent stromal cells during co-culture. Conversely, Cav-1 expression in fibroblasts can be rescued by administration of NAC or by overexpression of BRCA1 in HCC1937 cells. Notably, BRCA1-deficient human breast cancer samples (9 out of 10) also showed a glycolytic stromal phenotype, with intense mitochondrial staining specifically in BRCA1-deficient breast cancer cells. In summary, loss of BRCA1 function leads to hydrogen peroxide generation in both epithelial breast cancer cells and neighboring stromal fibroblasts, and promotes the onset of a reactive glycolytic stroma, with increased MCT4 and decreased Cav-1 expression. Importantly, these metabolic changes can be reversed by antioxidants, which potently induce cancer cell death. Thus, antioxidant therapy appears to be synthetically lethal with a BRCA1-deficiency in breast cancer cells and should be considered for future cancer prevention trials. In this regard, immunostaining with Cav-1 and MCT4 could be used as cost-effective biomarkers to monitor the response to antioxidant therapy.     

综述: 代谢重编程在调控肿瘤免疫微环境中的作用

肿瘤免疫治疗的成功揭示了宿主免疫在抵抗癌细胞增殖方面的重要作用以及抗肿瘤免疫治疗的可行性．但是具有免疫抑制作用的肿瘤微环境仍然是限制肿瘤免疫治疗进展的重要瓶颈．肿瘤微环境会诱发肿瘤细胞代谢发生重编程,此过程会导致肿瘤细胞与宿主免疫细胞竞争利用营养物质,肿瘤细胞来源的代谢产物或废物可通过多种方式影响免疫细胞的激活及效应功能的发挥,最终达到促使肿瘤细胞存活及增殖的目的．因此,本文就微环境条件下肿瘤细胞代谢重编程及其代谢产物对免疫微环境的影响展开讨论,以期为肿瘤免疫治疗提供理论基础及新的思路．     

Understanding the role of stromal fibroblasts in cancer progression

The major cellular components of tumor microenvironment, referred to as the cancer stroma, are composed of cancer-associated fibroblasts that support tumor epithelial growth, invasion and therapeutic resistance. Thus when we speak of developing therapies that address tumor heterogeneity it is not only a matter of different mutations within the tumor epithelia. While individual mutations in the stromal compartment are controversial, the heterogeneity in fibroblastic population in a single tumor is not up for debate. Cooperative interaction among heterotypic fibroblasts and tumor cells contribute to cancer progression. Therefore to tackle solid tumors, we need to understand its complex microenvironment. Here we review some seminal developments in the field of tumor microenvironment, mainly focusing on cancer-associated fibroblast.     

Understanding the role of stromal fibroblasts in cancer progression

The major cellular components of tumor microenvironment, referred to as the cancer stroma, are composed of cancer-associated fibroblasts that support tumor epithelial growth, invasion and therapeutic resistance. Thus when we speak of developing therapies that address tumor heterogeneity it is not only a matter of different mutations within the tumor epithelia. While individual mutations in the stromal compartment are controversial, the heterogeneity in fibroblastic population in a single tumor is not up for debate. Cooperative interaction among heterotypic fibroblasts and tumor cells contribute to cancer progression. Therefore to tackle solid tumors, we need to understand its complex microenvironment. Here we review some seminal developments in the field of tumor microenvironment, mainly focusing on cancer-associated fibroblast.