EMT理论的建立对单细胞侵袭作了充分阐述，但集体侵袭是组织学上更为常见的现象，集体侵袭中肿瘤细胞需兼有移动性和相互粘接双重特性，与EMT理论看似存在矛盾。在神经嵴发育、伤口愈合和肿瘤侵袭的最新研究显示，集体迁移领导细胞存在不同EMT状态，领导跟随细胞共同促进集体侵袭，为破解集体侵袭与EMT看似矛盾的难题提供有力证据。本课题在原有研究EMT与涎腺腺样囊性癌（ACC）关系基础上，提出科学假设：涎腺腺样囊性癌领导细胞不同EMT状态时空转化在集体侵袭中发挥重要作用。围绕此假设，拟采用时差DIC显微成像、活细胞工作站、单细胞分辨等技术，研究ACC集体侵袭中领导细胞EMT状态及时空转换特点，筛选领导细胞特异性标记物及其对EMT状态的影响，研究肿瘤基质微环境对领导细胞EMT状态时空转换和集体侵袭的影响，从而探索领导细胞不同EMT状态时空转换调控集体侵袭分子机制，结果将为临床防治ACC侵袭转移提供新策略。

Studies of epithelial-mesenchymal transitions (EMT) have traditionally focused on the migration of individual cells. However, histomorphologically, the most frequently observed invasion unit is a cell group whose collective behavior defines malignant function, that is, collective cell migration. And tumor cells in collective migration have both the motile and the cell-cell adhesion, which seems paradoxical with EMT theory. Importantly, the studies in the field of neural crest cells, wound healing and tumor invasion demonstrated that leader cells of collective migration could have different EMT states, and leader cells contribute to collective migration in coordination with follower cells, which provides a new clue to elucidate the relationship between EMT and collective invasion. Thus, owing to these evidences and our previous data in the relationship between EMT and the invasion and metastasis of adenoid cystic carcinoma(ACC), we hypotheses that the spatiotemporal regulation of different EMT states in leader cells play a critical role in collective migration of adenoid cystic carcinoma. In this project, time-lapse DIC microscopy, and three-dimnesional (3D) assay, live cell imaging system, and single-celled resolution technology will be applied to investigate the different states of epithelial, mesenchymal and intermediate phenotypes of leader cells and their characteristic of the spatiotemporal regulation, the specific biomarkers of leader cells and their modulating EMT states, as well as the role of extracellular matrix in the process of different EMT states of leader cells guiding the collective migration. The resolve to address these problems may elucidate the mechanism of EMT states spatiotemporal of leader cells regulating collective invasion of adenoid cystic carcinoma, and yield new therapeutic targets to the medication prevention of ACC invasion and metastasis in the future.