ITSN1-S（intersectin1-s)是ITSN1蛋白的短链亚型，被认为是胞浆表达蛋白并参与胞吞胞吐及细胞内多种信号通路。本课题组的前期研究成果显示ITSN1-S对调控肿瘤细胞的侵袭和凋亡具有重要作用（详见工作基础）。我们的深入研究又发现ITSN1-S在正常乳腺和良性病变组织的导管上皮无表达或仅有微弱表达，但在乳腺浸润性导管癌（IDC）的肿瘤细胞中表达明显增高；并且除了肿瘤细胞的胞质显著着色外，部分病例中出现ITSN1-S的胞核着色。这一结果也在我们的乳腺癌细胞株实验中得到验证（详见工作基础）。ITSN1-S在细胞核中的定位及其功能尚未见报道。本课题组将在这一新发现的基础上，利用乳腺癌临床样本进一步确认ITSN1-S的胞核定位并初步揭示其胞浆/胞核异位表达在乳腺癌中的临床意义，同时运用分子生物学、细胞学手段及动物实验等方法探讨ITSN1-S入核的分子调控机制及其功能。

ITSN1-S（intersectin1-s) is the short form of the protein ITSN1, it is regarded as a cytoplasm protein which is involved in endocytosis, exocytosis and cell signaling pathways. Our previous results indicated that ITSN1-S is a critical regulator in tumor invasion and apoptosis. Our further research discovered that ITSN1-S was rarely expressed in normal breast tissues and benign tissues, while there was more expression in IDC (invasive duct carcinoma). It is important that some tissues showed the expression of ITSN1-S in nuclei and this phenomenon was also confirmed in our experiments by breast cancer cell lines. Until present, rare results about nuclear expression of ITSN1-S are reported. In this project, our group will continue to focus ITSN1-S protein and to confirm the localization of ITSN1-S in nucleus. Meanwhile, we will apply clinic breast cancer tissues and determine the association of nuclear expression of ITSN1-S and clinical significance. Furthermore, we will explore the molecular mechanisms of translocation of ITSN1-S to nucleus and its function by a variety of molecular techniques in vitro and in vivo.