三阴性乳腺癌由于高转移率以及缺少靶向治疗成为生存率最低的一种乳腺癌。目前认为, CCL2对巨噬细胞的招募与激活与乳腺癌转移密切相关,而E3泛素连接酶CHIP在三阴性乳腺癌中表达降低或者丢失。前期研究表明三阴性乳腺癌细胞中过表达CHIP能调节ISGF3等转录因子活性，且使ISGF3下游基因CCL2分泌明显降低,提示乳腺癌细胞泛素化修饰与巨噬细胞招募与活化存在着关联。由此我们假设CHIP通过泛素修饰降低ISGF3稳定性, 下调CCL2蛋白表达，降低乳腺癌组织中巨噬细胞的侵润，抑制三阴性乳腺癌转移。本研究将（1）对乳腺癌组织中CHIP表达水平与巨噬细胞侵润及活化进行相关性分析；（2）鉴定乳腺癌细胞中招募巨噬细胞并且被ISGF3调控的细胞因子；（3）研究CHIP对ISGF3泛素化修饰的机制。本课题从肿瘤微环境的角度研究三阴性乳腺癌转移机理，揭示泛素修饰在肿瘤微环境调节方面重要的作用。

Triple negative breast cancer has the lowest survival rate among the breast cancers due to high metastases and lacking of targeted therapies. Recently, macrophage recruitment and activation by CCL2 are thought to be correlated with breast cancer metastasis, and E3 ubiquitin ligase CHIP is either down-regulated or lost in triple negative breast cancer tissues. Our previous work demonstrated that CHIP could regulate transcription factors’ activities through ubiquitination, among which ISGF3 was down-regulated and its downstream gene CCL2 was also decreased in triple negative breast cancer cells, which indicated ubiquitination may be involved in macrophage recruitment in breast cancer. We hypothesize that CHIP could suppress triple negative breast cancer metastases by down-regulating the recruitment of macrophages through ISGF3/CCL2 axis. In this project we will (1) investigate the correlation between CHIP and macrophage infiltration and activation in breast cancer tissues; (2) identify cytokines/chemokines regulated by CHIP through ISGF3 which recruit macrophages; (3) demonstrate the mechanism of ISGF3 ubiquitination by CHIP. The result of this project will give a novel explanation to the suppression of triple negative breast cancer metastases by CHIP through a perspective of tumor microenvironment change and also demonstrate an important role of ubiquitination in tumor microenvironment regulation.