乳铁蛋白调控肿瘤微环境的机制研究

Lactoferrin (LF) is a key component of innate immune defense. Based on the supporting from the NSFC, we previously reported that lactoferrin has anti-tumor and anti-metastatic activities in different cancers as well anti-inflammation function. We have constructed an Lf gene knockout mouse model to fulfill the in vivo functional study. By employing a tumor metastasis mouse model, we recently discovered that Lf knockout mice are more susceptibility for tumor metastasis comparing to the wild type mice. We also noticed there are more infiltration neutrophils existed in the metastasis loci, and the B-cell related function is also compromised in the Lf knockout mouse compared with wild type mice. Gene expression profiling revealed that the differential expressed genes induced by Lf knockout are mainly related to the neutrophils and B-cell functions, as well a few of metastasis associated genes such as Gpnmb. Tumor microenvironment has a crucial impact on the tumor metastasis. In this proposal, we will employ the Lf knockout mouse to making tumor metastasis model and to studying the effect of Lf deficiency (1) on the infiltration neutrophils, and (2) the B-cell function, and (3) the inhibition of T-cell function induced by Gpnmb-SD-4 axis. We believe our proposal will identify new mechanisms that are used by lactoferrin to modulate tumor microenvironment. This study will pave the way to understand the lactoferrin’s role in tumor metastasis translational medicine.

申请人的前两个国自项目发现了天然免疫分子乳铁蛋白具有抑癌基因的特征，能够抑制EB病毒感染，具有抗炎、抗肿瘤转移的功能，并构建了乳铁蛋白基因敲除小鼠。利用肿瘤转移小鼠模型，我们新近发现乳铁蛋白敲除小鼠的肿瘤转移灶明显增多，转移部位中性粒细胞浸润增多，B细胞增殖受到影响；基因表达谱分析：差异基因主要与中性粒、B细胞的功能相关，以及转移相关基因Gpnmb。肿瘤微环境对肿瘤转移产生重要影响，我们在本项目中将利用乳铁蛋白基因敲除小鼠，通过肿瘤转移模型，分析乳铁蛋白缺失之后如何影响肿瘤微环境中的中性粒细胞、B细胞功能，以及Gpnmb-SD4通路对T细胞功能的抑制。本项目将有助于回答：乳铁蛋白作为天然免疫分子，参与肿瘤微环境的调控机制；乳铁蛋白的临床检测和转化对于肿瘤转移防治的价值。

我们利用乳铁蛋白基因敲除（Lf-/-）小鼠模型，研究乳铁蛋白缺失对于肿瘤微环境、肿瘤转移的影响和调控机制。我们发现在Lf-/-小鼠中，肿瘤肺转移能力显著增强。乳铁蛋白缺失之后，小鼠肺组织中PMN-MDSC细胞比例显著增加，具有抑制T细胞的功能。而其涉及的信号通过中，TLR9通路被影响最多。通过一系列干预实验，发现针对MDSC细胞的中和抗体，服用乳铁蛋白，采用TLR9的激动剂，都能够逆转这一恶性表型。这个发现揭示了天然免疫分子乳铁蛋白与肿瘤远处的关系，即可通过影响肿瘤转移前龛MDSC细胞合成、分化，而影响肿瘤远处转移，并发现了重要的干预靶点。.此外我们还发现，乳铁蛋白可通过调控B细胞早期发育重要转录因子，以及对骨髓基质微环境的影响来影响B细胞早期发育，在骨髓B细胞发育的“土壤”和“种子”层面发挥不同的作用；在狼疮疾病模型中，乳铁蛋白基因敲除小鼠症状更重，口服乳铁蛋白可减轻症状，这与乳铁蛋白调控B细胞产生自身抗体的机制有关。乳铁蛋白缺失会影响骨髓微环境组分及B细胞早期分化相关转录因子的表达，使B细胞早期发育出现障碍。乳铁蛋白在系统性红斑狼疮疾病模型中对机体发挥保护性作用。.本项目整体研究内容充实，充分揭示了天然免疫分子乳铁蛋白对于肿瘤转移的抑制作用和机制；发现了乳铁蛋白对于B细胞早期发育的影响和分子机制，这对于利用乳铁蛋白来预防肿瘤转移和B细胞发育相关性疾病，具有较重要的转化价值和研究价值。