肿瘤相关巨噬细胞（TAMs）呈M2型巨噬细胞表型，具有诱导细胞恶性转化和促进肿瘤转移等作用，但诱导其M2极化及功能变化的分子机制尚未明确。我们在前期工作中证实高分级胃癌TAMs中EGFR活化水平较低分级肿瘤降低；特异性敲除巨噬细胞的EGFR，可促进IL-4诱导的M2极化；提示EGFR信号具有调控巨噬细胞分化及功能的作用。因此提出研究假设：巨噬细胞中EGFR信号活化，可抑制其M2极化,下调其促肿瘤生长和转移的作用。本研究将检测胃癌患者TAMs中EGFR的活化状态，分析与临床指标、胃癌细胞IL-11,ptger4,TGF-β表达和Wnt信号活化的关系；下调巨噬细胞EGFR表达及活化水平，观察对巨噬细胞M2极化及STAT6活化的影响；调控巨噬细胞EGFR信号，观察其影响胃癌细胞生长及上皮间质转化（EMT）作用的变化。为探讨TAMs在细胞恶性转化以及肿瘤生长和转移中的作用及调控机制奠定基础。

Tumor microenvironment is an important aspect of gastric cancer and other cancer development. Tumor-associated macrophages (TAMs) produce mediators in the tumor microenvironment to promote cell malignant transformation,tumor angiogenesis, immunosuppression, and metastasis. TAMs are predominantly polarized to M2 macrophage phenotype. Epidermal growth factor receptor (EGFR) activation in tumor cells accelerates tumorigenesis. However, therapy to inhibit EGFR activity is not universally efficacious, suggesting possible widespread resistance of tumor cells to EGFR inhibition or EGFR in other cell types exerts different functions. Our preliminary data show that activation of EGFR in macrophages down-regulates IL-10 production and up-regulates TNF in response to inflammatory stimuli. EGFR activation level in TAM is higher in low-grade than that in high-grade gastric cancer tissues from patients. Furthermore, we find that IL-4 transactivates EGFR in macrophages, which is required for inhibiting IL-4-induced Arg1, a M2 marker expression and suppressing production of mediators for gastric cancer cell growth. Therefore, our overall objective is to understand the effects and mechanisms of by which EGFR in TAMs regulates gastric tumor development. We hypothesize that EGFR activation in TAMs inhibits TAM's effects on gastric cancer development. First, will further confirm that EGFR is activated in TAMs in gastric cancer tissues isolated from patients, and determine the relationship between the level of EGFR activation in TAMs and gastric tumor grade, expression of gastric cancer related genes, and activation status of signaling involved in promoting gastric cancer progress. Second,we will determine the role of EGFR in macrophages in induction of M2 macrophages. We will define the role of EGFR in induction of M2 macrophages by IL-4 or IL-13 and STAT6 activation using induced human and mouse macrophages.EGFR expression in human macrophages will be knocked down using a siRNA transfection method. We will use peritoneal macrophages isolated from mice with EGFR specifically deleted from macrophages. Third, we will determine the role of EGFR in macrophages in regulation of gastric cancer cell growth and epithelial-to-mesenchymal transition (EMT). We will use supernatants from induced M2 macrophageswith or without EGF expression to culture a novel ex vivo mouse gastric organoid system and human gastric cancer cells, respectively. Factors which are produced by IL-4 or IL-13 induced M2 macrophahes in an EGFR-dependent manner will be analyzed using shotgun proteomics and confirmed by their gene and protein expression levels. Results from this project will provide information to elucidate how cell specific EGF receptor activation regulates tumor microenvironment for tumorigenesis. These studies will be a critical step towards translating these observations into the next generation predictors of disease or therapeutics for gastric cancer.