The Mechanisms of GM-CSF Inhibition of Breast Cancer Growth and Metastasis

描述（由申请人提供）：本提案重点了解gm - csf诱导单核吞噬细胞产生sVEGFR-1的机制及其抗肿瘤活性。我们的数据表明，当正常的FVB/N雌性小鼠注射PyMT肿瘤细胞并形成肿瘤时，局部注射rmGM-CSF可显著抑制肿瘤生长，转移到肺部，肿瘤内的氧气，并提高小鼠的总体存活率。我们的假设是GM-CSF会诱导驻留在乳腺肿瘤中的单核细胞和巨噬细胞产生并释放可溶性形式的VEGF受体-1 （sVEGFR-1）。这种诱骗受体是膜结合的VEGFR-1的交替剪接变体，它结合并隔离VEGF的生物活性。VEGF对维持内皮细胞存活和正常血管床至关重要，随着肿瘤环境中VEGF的减少，肿瘤血管系统将分解，导致肿瘤内的模式坏死，最终导致肿瘤细胞死亡。我们在Matrigel栓子实验中发表了这些影响，并显示栓子内血管生成减少。本研究的初步数据表明，GM-CSF在小鼠乳腺癌模型中显著降低肿瘤生长和转移，部分原因是通过抑制肿瘤的可用氧。通过评估GM-CSF在人类肿瘤环境中的作用来进一步研究这些发现是至关重要的。我们将使用免疫缺陷、胸腺发育的裸雌性小鼠与MCF10A、MCF10AT1k、MCF10CA1h和MCF10CA1a人类肿瘤细胞系一起观察这些影响。这些细胞系是永活的乳腺上皮细胞，在注射到裸鼠乳腺脂肪垫时具有致瘤性，并且在转移性方面各不相同。

DESCRIPTION (provided by applicant): This proposal focuses on understanding the mechanism of GM-CSF-induced sVEGFR-1 production from mononuclear phagocytes and the resulting anti-tumor activity therein. Our data indicates when normal FVB/N female mice are injected with PyMT tumor cells and form a tumor, local injection of rmGM-CSF significantly inhibits tumor growth, metastases to the lung, oxygen within the tumors, as well as increases overall survival of the mouse. Our hypothesis is that GM-CSF will induce the monocytes and macrophages, which reside in mammary tumors, to produce and release the soluble form of the VEGF receptor-1 (sVEGFR-1). This decoy receptor is an alternately-spliced variant of the membrane-bound VEGFR-1 that binds and sequesters VEGF from biological activity. With reduced VEGF in the tumor environment, which is essential in maintaining endothelial cell survival and normal blood vascular beds, the tumor vasculature will break down and result in patterned necrosis within the tumor and eventual tumor cell death. We have published these effects in vivo in a Matrigel plug assay and show reduced angiogenesis within these plugs. Preliminary data in this proposal suggest that GM-CSF significantly reduces tumor growth and metastases in a murine model of breast cancer, in part, by inhibiting the available oxygen to the tumor. It is essential to further these findings by evaluating the effects of GM-CSF in a human tumor environment. We will be using immunodeficient, athymic nude female mice in conjunction with MCF10A, MCF10AT1k, MCF10CA1h and MCF10CA1a human tumor cell lines to see these effects. These cell lines, tumorigenic when injected into the mammary fat pad of nude mice, are immortalized mammary epithelial cells and vary in metastatic aggressiveness. Thus the Specific Aims will address the following questions: Aim 1. To determine the effect of GM-CSF-induced sVEGFR-1 on angiogenesis and metastases in breast tumors. Aim 2. To determine the cells responsible for sVEGFR-1 production in response to GM-CSF. Aim 3. Does GM-CSF inhibit tumor growth, angiogenesis, and metastases of human tumors in nude mice? We anticipate the findings from these studies will provide novel insight in the mechanisms of tumorassociated cells, in this case mononuclear phagocytes, and the potential to change their phenotype from that of tumor-supporting to that of tumor-suppressive.