Hsc70介导的L1核转运机制及其在肿瘤发生、侵袭转移中的生物学功能研究

L1 cell adhesion molecule (L1-CAM) plays a major role in the development of the nervous system, and in the proliferation, tumorigenesis, tumor invasion, and angiogenesis in human tumors. Most of studies focus on the functions of L1 ectodomain in tumorigenesis and tumor invasion, they found that the ectodomain can activate ERK and NF-κB signaling pathway, which regulate the expression of tumor-related genes consequently. However, recent studies demonstrated that the abnormal expression of L1 in the cytoplasm and nucleolus, which was associated with tumor prognosis and malignancy. Therefore, we expected that the L1 intracellular domain (L1-ICD) might interact with some molecular in cytoplasm (and/or nucleolus), and then activate the tumor-related signaling pathways, which can regulate the process of tumorigenesis and tumor invasion. In this study, we found that Hsc70 protein can interact with L1-ICD directly, which then mediate the L1 nuclear translocation. And we also found that L1 may bind to LEF/TCF, which is a tumor-related transcription factor, to compose a complex to up-regulate the transcription of Snail, Slug, and Twist. We think that L1 functions may be associated with tumorigenesis and tumor invasion. The clarification of the nuclear translocation of L1 and its significance for tumorigenesis and tumor invasion will extend our understanding for the relationship between L1 and tumor.

神经粘附分子L1在肿瘤发生、侵袭转移过程中，被广泛认为可能是通过水解产生的L1胞外端激活ERK和NF-κB信号通路发挥其生物学功能。然而，有研究发现在肿瘤组织中，L1在细胞质和细胞核中表达异常，并且与肿瘤的预后及恶性程度的有着密切的联系。因此我们推测L1胞内端可能通过与相关分子结合，继而在胞质（或胞核）内激活肿瘤相关信号通路，最终对肿瘤的发生、侵袭转移进行调控。本项目拟利用蛋白质谱、Co-IP、EMSA、生化技术等研究手段，研究L1与Hsc70的相互作用，以及Hsc70介导的L1核转运分子机制。同时，我们还发现L1可能与LEF/TCF组成转录复合体，激活并上调肿瘤相关因子Snail、Slug及Twist的表达水平，从而对肿瘤的发生、侵袭转移发挥其生物学功能。对这一新机制的阐明，有助于拓展我们对L1在肿瘤发生、侵袭过程中的生物学功能的理解 ，并为以L1为靶点的肿瘤临床诊断与治疗提供理论依据。

该项目为阐明Hsc70介导的L1核转运机制，从而为恶性胶质瘤提供潜在的诊疗靶点，本项目在项目执行期间顺利实施，主要研究成果如下：① 阐明了Hsc70介导L1的核转运机制，并发现L1表达水平及核转运水平与胶质瘤恶性程度和患者预后密切相关（主要研究结果拟投稿Nature Communications）；② 我们发现L1可以与CD24和Heparanase组成复合体，该复合体与胶质瘤预后密切相关（Barash U, et al. International Journal of Cancer 2019; 145:1596-1608）；③ 在模式生物斑马鱼中利用Crispr/Cas9建立无缝插入基因的基因编辑技术 （Luo JJ et al. The FASEB Journal 2018; 32:5132-5142）; ④研究发现在NSCLC中，EHMT2通过调控PTEN/AKT信号通路促进了EGFR-TKI抗药性（Wang LH et al. Cell Death & Disease 2018; 9:129）; ⑤ 发现Par6可以通过激活Akt/PI3K/GSK-3β信号通路调控胶质瘤细胞周期，进而促进胶质瘤的发生（Liu P et al. The FASEB Journal, In Press）。