NG2-PG in tumor vascularization and progression

在小鼠乳腺肿瘤病毒启动子（MMTV-PyMT）控制下，表达多瘤中间T癌蛋白的雌性转基因小鼠100%发生多灶性乳腺肿瘤。在MMTV-FyMT模型中，通过包括肿瘤潜伏期、生长速度和转移在内的几个标准，基因消融横跨膜的NG2蛋白多糖大大减缓了乳腺肿瘤的进展。虽然NG2在MMTV-PyMT小鼠的乳腺肿瘤细胞中不表达，但它在肿瘤基质中的三种重要细胞类型中表达：肿瘤微血管中的周细胞、乳腺脂肪垫中的脂肪细胞和从循环侵入肿瘤的巨噬细胞。因此，我们假设NG2对血管形成、脂肪生成和巨噬细胞募集的影响可能通过改变肿瘤细胞与这三种关键基质元素的相互作用来影响乳腺肿瘤的进展。这一缩短版ARRA提案的具体目的是在MMTV-PyMT模型中检测微血管NG2和巨噬细胞NG2对乳腺肿瘤血管化和进展的各自影响。

100% of female transgenic mice expressing the polyoma middle T oncoprotein under control of the mouse mammary tumor virus promoter (MMTV-PyMT) develop multifocal mammary tumors. By several criteria, including tumor latency, growth rate, and metastasis, genetic ablation of the membrane-spanning NG2 proteoglycan greatly slows mammary tumor progression in the MMTV-FyMT model. Although NG2 is not expressed by mammary tumor cells in the MMTV-PyMT mouse, it is expressed by three important cell types in the tumor stroma: pericytes in the tumor microvasculature, adipocytes in the mammary fat pad, and macrophages that invade tumors from the circulation. We therefore hypothesize that effects of NG2 on vascularization, adipogenesis, and macrophage recruitment may affect mammary tumor progression by altering tumor cell interactions with these three key stromal elements. The specific aims of this shortened ARRA version of the proposal will be to examine the respective effects of microvascular NG2 and macrophage NG2 on mammary tumor vascularization and progression in the MMTV-PyMT model. In Aim 1, we will compare the tumor vascularization patterns seen in wild type and NG2 nulFrriice oñ the MMTV-P7MT baökgroUnd. Thi'MTF iñciuddéth Tntiöñ dfVàëUIàr fUhcf[oh (patency, basal lamina deposition, tissue hypoxia), morphology (tortuousity), and density, along with examination of pericyte/endothelial cell relationships leading to maturation of both cell types. We will also use Pdgfrb/Cre transgenic mice, in conjunction with a floxed NG2 allele, to generate a pericyte-specific NG2 null mouse. Mammary tumor progression in this mouse on the MMTV-PyMT background will more fully illuminate the pericyte-specific effects of NG2 on tumorigenesis. In Aim 2 we will study the role of NG2 in macrophage-dependent tumor progression. This will include the recruitment of macrophages to developing tumors, and the role of macrophages in tumor vascularization, tumor cell intravasation, and tumor metastasis. We will also produce a macrophage-specific NG2 knockout mouse on the MMTV-PyMT background, using the lysozyme M/Cre mouse in conjunction with a floxed NG2 allele. This model will reveal macrophage-specific effects of NG2 on mammary tumor vascularization and progression