分泌性SNCG促进肿瘤细胞恶性表型的分子机制研究

SNCG (synuclein-gamma), or breast cancer specific gene-1, is overexpressed in several cancer cells and its overexpression stimulates cancer metastasis and confers chemoresistance.The level of SNCG in a variety of human cancers correlats with TNM stages. Our previous work demonstrated that high expression of SNCG in colon and breast cancer tissues was a poor prognostic indicator. We recently found higher SNCG level in sera from patients with gastrointestinal and esophageal squamous cell carcinomas than in sera from benign patients and healthy people. Combination of SNCG with CEA and/or CA19-9 obviously increased the positive diagnosis rate of cancer. SNCG can be secreted by MCF-7 cells stably transfected with SNCG or GFP-SNCG and by HT-29 colon cancer cells expressing high level of endogenous SNCG. Our preliminary results have showed SNCG can be detected in both soluble and membrane fractions of cell culture supernatant,suggesting that SNCG is secreted, at least in part, in association with membrane vesicles that have the hallmarks of exosomes. Exogenous SNCG added to cell culture medium can be detected on cell membrane of the recipient cells and enhance cell migration,invasion and colony formation,indicating pathogenic actions of SNCG extend to the extracellular space and neighboring cells. Up to now, the mechanism of cytoplasmic SNCG being released to the circulating system is still elusive, and the biological function of the releasing SNCG in extracellular environment also needs to be investigated. We will intensively address the above issues by in vitro and in vivo assays to uncover the molecular mechanism of secreted SNCG in tumourigenesis and malignant progression. Also, a novel microenvironmental SNCG may result in the development of additional cancer treatment modalities in the control of cancer aggressiveness and progression.

近年研究表明，SNCG（Synuclein-γ）可促进肿瘤细胞侵润、转移及对化疗药物抗性，多种肿瘤组织SNCG高表达并同病理分期相关。我们的研究表明，SNCG高表达是判断乳腺癌、结肠癌患者预后不良的独立指标；用双抗夹心ELISA法检测发现，与正常和相应良性病变人群相比，结直肠癌、胃癌、食管癌等患者血清SNCG水平明显升高，而且与CEA水平有较好的互补性，同时发现肿瘤细胞有可能通过外泌体途径分泌SNCG，分泌的SNCG可以与肿瘤细胞膜结合并促进其迁移、侵袭和克隆形成。本项目拟在上述工作基础上，通过进一步的深入研究，明确SNCG分泌到胞外的确切机理及影响其分泌的相关因素、阐明SNCG促进肿瘤细胞恶性表型的主要分子机制及相关的调控网络，以期为全面认识SNCG在肿瘤发生发展中的作用、获得有可能用于临床的新的肿瘤标志物及研发针对细胞外SNCG的靶向药物治疗提供一定的理论和实验依据。

近年研究表明，SNCG（Synuclein-γ）可促进肿瘤细胞侵润、转移及对化疗药物抗性。SNCG高表达是判断乳腺癌、结肠癌患者预后不良的独立指标；与正常和相应良性病变人群相比，结直肠癌、胃癌、食管癌等患者血清SNCG水平明显升高，而且与CEA水平有较好的互补性。我们前期工作发现胞浆蛋白SNCG可分泌到胞外，且可与肿瘤细胞膜结合并促进其迁移、侵袭。.本项目主要研究内容是：确定胞浆蛋白SNCG分泌到细胞外的机理；在体内、外进一步证实分泌性SNCG促肿瘤细胞的侵袭、转移作用；SNCG促肿瘤细胞恶性表型的机理探讨。.我们研究发现：胞浆蛋白SNCG是以非传统途径分泌到胞外，SNCG分泌不受传统途径分泌的抑制剂BFA的影响，而非传统途径分泌的外泌体途径、溶酶体途径的抑制剂可明显抑制SNCG的分泌。PI3K抑制剂、akt抑制剂等也明显抑制SNCG的分泌，提示SNCG分泌也受PI3K/Akt信号通路的影响。证实了胞内SNCG以游离形式和与囊性/膜性结构结合的形式存在,此结果也支持了SNCG从胞内到胞外分泌过程中存在的SNCG中间体形式。发现定位于细胞膜的SNCG可与flotillin-2相互结合,而Flotillin-2与细胞内膜转运相关，也证实了细胞内SNCG动态变化的现象。天然分泌性SNCG (HT-29细胞上清) 和重组表达的SNCG对肿瘤细胞的生长没有影响，但均能促进肠癌肿瘤细胞系HT-29、HCT-116、LOVO的迁移和侵袭，降低肿瘤细胞的粘附，而对非癌细胞几乎没有影响。发现胞外SNCG使肿瘤细胞培养上清中MMP-24、Annexin-2、HSP-70量明显升高，提示胞外SNCG可能改变肿瘤细胞微环境。本研究还发现，胞外SNCG能通过与细胞膜β1-integrin 结合上调p-FAK(Y925)的活性并引起细胞内、外多个蛋白分子的变化进而促进肿瘤细胞的恶性表型，此现象在小鼠模型和肿瘤组织中也获得了验证。.本项目的实施丰富了人们对SNCG在肿瘤发生发展中的作用及相关机制的认识，部分研究结果已发表SCI 研究论文3篇、同时应邀为并应邀为Methods Mol Biol系列丛书Unconventional Protein Secretion撰写了相关章节。