ALCAM参与头颈鳞癌干细胞干性调控的分子机制及其靶向治疗

Stemness traits are the distinctive feature of stem cells. Compared with normal stem cell, stemness ability of cancer stem cells are some kind of out of control, which drives the continuing growth, recurrent and metastasis of cancers. It is of importance to understanding their biologic mechanisms and finding a possible targeting method on these cancer stem cells. Our group has studied the specific membrane protein on the cancer stem cell from head and neck squamous cell carcinoma(HNSCC) with membrane proteomic analysis. We found that activated leukocyte cell adhesion molecule (ALCAM) expression was closely related to the stemness traits of cancer stem cells. It not only can be used as a cell surface biomarker to enrich cancer stem cell from HNSCC, but also can promote the activation of classic wnt and hedgehog pathways. Patients whose tumor expressed higher level of ALCAM generally had a poor prognosis. ALCAM may act as an ideal therapy target for cancer stem cells of HNSCC. Till now, the underlying function of ALCAM in cancer stem cells and its downstream molecules are not clear. We also don't know how it is regulated in cancer stem cells. So the aim of this project is to investigate the basic function of ALCAM in cancer stem cell and its regulation method, looking for its downstream and upstream molecules, and the final aim is to identify its potential value as the therapeutic target of HNSCC.

干性是干细胞的本质特征。肿瘤干细胞的异常干性驱动着肿瘤生长、复发和转移。研究其干性调控方式对寻找靶向肿瘤干细胞的治疗方法具有重要意义。我们前期以头颈鳞癌细胞作为研究模型，用蛋白质组技术筛选癌干细胞特征性膜蛋白标志物时发现，活化白细胞黏附分子（ALCAM）的表达水平和癌干细胞的生物学行为密切相关：ALCAM不仅是头颈鳞癌干细胞表面分子标志物之一，它还参与细胞干性的维持，促进wnt及hedgehog信号通路激活。ALCAM的表达水平与头颈鳞癌患者预后独立相关，提示ALCAM是一个理想的肿瘤干细胞治疗候选靶点；但目前对ALCAM参与肿瘤干细胞干性维持的具体分子机制及调控方式并不清楚。因此，本项目旨在已有工作基础上，深入研究ALCAM调节肿瘤细胞干性的分子机制，寻找ALCAM的下游作用分子及上游调节分子，从细胞模型、移植瘤模型和临床标本等不同层面，来探讨ALCAM作为口腔鳞癌干细胞治疗靶点可行性。

干性是干细胞的本质特征。肿瘤干细胞的异常干性驱动着肿瘤生长、复发、转移和耐药。研究其干性调控方式对寻找靶向肿瘤干细胞的治疗方法具有重要意义。课题组前期以口腔鳞癌作为研究模型，用蛋白质组技术筛选癌干细胞特征性膜蛋白标志物时发现，活化白细胞黏附分子（activated leukocyte cell adhesion molecule, ALCAM）的表达水平和癌干细胞的生物学行为密切相关：ALCAM不仅是头颈鳞癌干细胞表面分子标志物之一，它还参与细胞干性的维持，促进Wnt及Hedgehog信号通路激活。ALCAM的表达水平是口腔鳞癌患者预后独立因素，提示ALCAM是一个理想的肿瘤干细胞鉴定的候选靶点；目前对ALCAM参与肿瘤干细胞干性维持的具体分子机制及调控方式并不清楚。因此，本项目在已有工作基础上，深入研究ALCAM调节肿瘤细胞干性的分子机制，寻找ALCAM下游作用分子及上游调节分子，从细胞模型、移植瘤模型和临床标本等不同层面，来探讨ALCAM作为口腔鳞癌干细胞治疗靶点可行性。1. 蛋白免疫共沉淀结合蛋白质谱分析筛选鉴定到一系列ALCAM结合膜蛋白，包括EGFR；随后经体内外实验证实，ALCAM能够通过与EGFR的结合影响EGF/EGFR信号通路的活化、pEGFR的泛素化和降解，还影响下游信号通路的活化及细胞骨架的改变，进而影响肿瘤细胞的克隆形成能力和迁移能力，并对其体内成瘤能力产生影响；2.临床肿瘤标本中分选ALCAM+及ALCAM-的细胞，比较其克隆形成能力，裸鼠体内连续成瘤能力具有显著差异；3. 大样本信号通路芯片检测发现，口腔鳞癌内ALCAM的表达水平与Hedgehog信号通路关键分子Gli1及Gli2的表达水平显著相关；进一步研究发现，ALCAM和Hedgehog信号通路间存在相互调控关系，Hedgehog信号通路活化稳定ALCAM的表达，进而增强肿瘤细胞的转移能力。