TNF-Mediated Tumor Promotion: The Role of Vascular Leukocytes

描述(由申请人提供)： 背景资料。最近，我们和其他人描述了大量与肿瘤相关的白细胞，它们共表达内皮细胞和髓系标志，即所谓的“血管白细胞”。大多数研究表明，它们是肿瘤生长和血管生成的强有力的介质。血管白细胞的产生可能受肿瘤微环境信号的调节。它们的产生机制尚不清楚。目的/假设：我们的初步数据表明，肿瘤坏死因子导致培养的单核细胞内皮细胞特异性标志物呈剂量依赖性上调。这种作用依赖于肿瘤坏死因子受体，因为从缺乏肿瘤坏死因子受体的小鼠分离的细胞在髓系/内皮双表型细胞的生成中表现出明显的延迟动力学。与对侧对照肿瘤相比，植入肿瘤坏死因子过多的小鼠含有更大、更多的血管肿瘤和更多的血管白细胞。基于这些令人兴奋的数据，我们假设局部来源的肿瘤坏死因子通过部分调节髓系/内皮双表型细胞的产生，是肿瘤生长的重要调节因子。具体目的：1)在小鼠肿瘤生长模型中，通过上调局部肿瘤来源的表达和通过骨髓移植模型的免疫阻断方法，确定肿瘤坏死因子在血管白细胞形成中的作用。2)阐明肿瘤坏死因子促进白细胞血管可塑性的机制(S)。与退伍军人退伍军人使命的相关性：癌症是我们老年退伍军人发病率和死亡率的主要原因。这笔赠款基于初步数据，这些数据支持一种新的假设，即肿瘤坏死因子的“促血管生成”和促肿瘤特性至少部分是通过促进髓系到内皮细胞的分化来调节的，这种分化直接导致乳腺癌和黑色素瘤皮肤癌中特定的促血管生成血管白细胞亚群。这项工作可能导致使用肿瘤坏死因子抑制剂作为辅助治疗，以操纵特定的髓系群体，以消除我们的退伍军人的肿瘤进展。 公共卫生相关性： 项目叙事。人们普遍认为，癌症生长的许多方面都是由炎症调节的。肿瘤坏死因子-α(TNF)是重要的炎症介质。它最初是从患有严重微生物引起的炎症的小鼠的血液中分离出来的，并被证明能导致肿瘤坏死或死亡(由此得名)。重要的是，在这样的实验中使用的肿瘤坏死因子的剂量非常大。然而，内源性肿瘤坏死因子是在肿瘤中长期、低水平产生的。最近的几项研究表明，在这些低剂量的慢性剂量下，肿瘤坏死因子促进了肿瘤的生长。例如，肿瘤坏死因子基因或其作用机制缺失的小鼠延缓了肿瘤的生长和转移。然而，我们对肿瘤坏死因子如何作为肿瘤促进剂的理解存在差距。我们的实验室长期以来一直在研究血管干细胞在癌症中的作用。我们和其他许多人已经证明，在体外和体内，髓系细胞可以上调内皮细胞标志物。这些髓系/内皮双表型细胞代表促进肿瘤生长和血管生长的髓系细胞亚群。使用表达略高水平的肿瘤坏死因子，我们有强有力的证据表明，肿瘤内至少有一个重要的机制是促进髓系/内皮细胞的分化。这些发现是全新的，对癌症治疗具有重要意义。肿瘤坏死因子抑制剂已经上市，并获得FDA批准，用于治疗炎症性疾病，如关节炎。通过了解肿瘤坏死因子在肿瘤-髓系细胞相互作用中的作用细节，我们可能能够开发使用肿瘤坏死因子抑制物的新的癌症治疗策略。癌症仍然是我们年迈的退伍军人中普遍存在的健康问题，对退伍军人事务部的生物医学研究任务至关重要。

DESCRIPTION (provided by applicant): Background. Recently, we and others have characterized a significant population of tumor- associated leukocytes which co-express endothelial and myeloid markers, the so called "vascular leukocytes". Most studies indicate that they serve as potent mediators of tumor growth and angiogenesis. Generation of vascular leukocytes is likely modulated by cues from the tumor microenvironment. The mechanism of their generation is not known. Objective/Hypothesis: Our preliminary data suggest that TNF results in a dose-dependent upregulation of endothelial-specific markers in cultured monocytes. This effect was dependent on TNF receptors as cells isolated from mice lacking TNF receptors displayed dramatically delayed kinetics in myeloid/endothelial biphenotypic cell generation. Mice implanted with TNF overproducing tumors contained larger, more vascular tumors with increased numbers of vascular leukocytes than contralateral, control tumors. Based on these exciting data, we hypothesize that locally-derived TNF is an important regulator of tumor growth by regulating, in part, the generation of myeloid/endothelial biphenotypic cells. Specific Aims: 1) Determine the role of TNF in vascular leukocyte formation in mouse models of tumor growth by upregulating local tumor-derived expression and by immunoblocking approaches with bone marrow transplant models. 2) Delineate the mechanism(s) by which TNF promotes vascular plasticity of leukocytes. Relevance to VA mission: Cancer is a leading cause of morbidity and mortality among our aging Veterans. This grant is based on preliminary data that support a novel hypothesis that the "proangiogenic" and tumor-promoting properties of TNF are mediated, at least partly, by facilitating myeloid to endothelial differentiation that contributes directly to specific proangiogenic vascular leukocyte subpopulations within both breast and melanoma skin cancers. This work may lead to the use of TNF inhibitors as adjunct therapy to manipulate specific myeloid populations to abrogate tumor progression in our Veterans. PUBLIC HEALTH RELEVANCE: PROJECT NARRATIVE. It is widely accepted that many aspects of cancerous growth is mediated by inflammation. Tumor necrosis factor-alpha (TNF) is an important mediator of inflammation. It was first isolated from the blood of mice suffering from severe microbial-induced inflammation and was shown to induce tumor necrosis or death (hence the name). Importantly, the doses of TNF used in such experiments were very large. Endogenous TNF, however, is produced at chronic, low levels in tumors. Several recent studies suggest that at these low, chronic doses, TNF promotes tumor growth. For example, mice that have a deletion in TNF gene or the machinery by which it acts, have delayed tumor growth and metastasis. However, there is a gap in our understanding on how TNF serves as a tumor promoter. Our laboratory has long studied the role of blood vessel stem cells in cancer. We and many others have shown that myeloid lineage cells can upregulate endothelial markers in vitro and in vivo. These myeloid/endothelial biphenotypic cells represent a subpopulation of myeloid cells that are promote tumor growth and blood vessels. Using tumors that express slightly higher levels of TNF, we have strong evidence that at least one important mechanism by which TNF works within tumors is by promoting the differentiation of myeloid/endothelial cells. These findings are entirely novel and have important implications in cancer therapy. TNF inhibitors are already available and FDA-approved to treat inflammatory disorders, such as arthritis. By understanding the details of TNF's role in tumor- myeloid cell interactions, we may be able to develop new cancer therapeutic strategies using TNF-inhibitors. Cancer continues to be a pervasive and prevalent health problem among our aging Veterans and critical to the biomedical research mission of the Veterans Affairs.