外泌体在肿瘤细胞迁移过程中发挥重要作用，外泌体表面覆盖大量糖缀合物，但糖基化修饰影响外泌体功能的研究尚不够深入。前期工作中申请人发现乳腺癌细胞平分型GlcNAc糖基化含量降低，过表达平分型GlcNAc抑制乳腺癌细胞MDA-MB-231的迁移和增殖，但平分型GlcNAc是否影响乳腺癌外泌体的功能未知。预实验证实231细胞外泌体表达整合蛋白β1，若外泌体过表达平分型GlcNAc，或添加β1中和抗体，都显著降低受体细胞MCF-7的迁移。据此本项目提出假设：整合蛋白β1的平分型GlcNAc修饰抑制受体细胞迁移和增殖等能力。项目将通过细胞模型和小鼠实验，研究乳腺癌细胞和乳腺癌病人血清样本中不同平分型GlcNAc修饰的外泌体对受体细胞迁移、增殖等影响，阐明乳腺癌外泌体上平分型GlcNAc修饰影响整合蛋白β1的活性进而改变受体细胞增殖和迁移的机制，以期为乳腺癌的诊疗提供科学依据。

Exosomes secreted by tumor cells can increase metastasis through interaction with cells of the microenvironment. The surface of exosomes is covered by glycoconjugates such as proteoglycans, glycosphingolipids and glycoproteins, whose function are known to be invovled in tumor progression. However, the functional role of glycans in exosomes is far less understood than that of proteins, lipids and nucleic acids. In our previous study, suppression of bisecting GlcNAc structures were observed in epithelial-mesenchymal transition (EMT), and high expression of bisecting GlcNAc by the overexpression of MGAT3 could inhibit hypoxia-induced EMT processin breast cancer cells. In this proposal, we are interested in the functional role of bisecting GlcNAc in breast tumor exosomes. Our preliminary data indicated that high expression of integrin β1 was detected in breast cancer cell-derived exosomes. The metastasis of recipient cells induced by breast cancer cell-derived exosomes were suppressed by high expression of bisecting GlcNAc on exosomes, or by the exogenous addition of neutralized integrin β1 antibody. Herein, we speculate that bisecting GlcNAc structures on exosomal integrin β1 could affect the bioactivity of integrin β1, and further suppress the enhanced migration and proliferation of recipient MCF-7 cells. This study will evaluate the expression of bisecting GlcNAcylation on the exosomes derived from breast cancer cells or from patients serum, and explore the effect of those exosomes on the metastasis and proliferation of recipient cells. This study will also define the molecular mechanism of how bisecting GlcNAc structures interfer with exosomal integrin β1 bioactivitiesand further suppress the carcinogenic capability of recipient cells. Taken together, this study will provide a valuable basis for diagnosis and therapy of breast cancerfor future studies.