肿瘤细胞中自身抗原Ro60调控p53的功能机制研究

As the key tumor suppressor, p53 is the master regulator of cell-intrinsic barrier (including cell cycle checkpoint, DNA damage repair, senescence and apoptosis) and cell-extrinsic barrier, which mediated by the immune system. It was reported that the incidence of malignancy is increased in systemic lupus erythematosus (SLE) patients. The Ro 60 kDa auto-antigen (Ro60) is the major target of the immune response in patients suffering SLE. Ro60 deficiency and anti-Ro60 antibody may be important in stimulating autoimmune and SLE. We identified recently that Ro60 inhibited proliferation and increased radio-sensitivity of tumor cells to γ-irradiation, and reduced expression of Ro60 mRNA was associated with p53 decrease in MCF-7 tumor cells and stomach malignancy samples. We also identified that Ro60 over-expression resulted in increase of p53 and the bona fide p53 target gene ULBP2 mRNA expression. ULBP2 is a ligand of NK cell receptor NKG2D (natural killer group2, member D), which is an important component of the front-line immune defense against malignancies. This proposes will study the function and regulatory mechanisms of auto-antigen Ro60 in p53 regulation in tumor cells, and analyze the relationship between Ro60 and the incidence of tumor in SLE patient, which will help us to identify the function of Ro60-p53 pathway in tumor immune, growth and sensitivity to anti-cancer therapy, and may help to propose new strategies in tumor diagnosis and therapy.

抑癌分子p53在细胞检查点激活、损伤修复、衰老、凋亡等细胞自身肿瘤监视机制和免疫系统构筑的胞外肿瘤监视机制中均发挥重要调控作用。自身免疫疾病系统性红斑狼疮（SLE）患者中肿瘤发生率显著增加。RNA结合蛋白Ro60是SLE患者免疫反应的主要靶分子之一，其功能异常与免疫调控异常、SLE病理发生密切相关。我课题组新研究发现： Ro60调控肿瘤细胞增殖和γ辐射敏感性；肿瘤细胞和临床胃癌组织样本中Ro60的mRNA下调与p53下调相关联,过表达Ro60促进肿瘤细胞中p53及p53下游肿瘤免疫激活靶分子ULBP2的mRNA表达。本申请拟在上述新发现的基础上研究肿瘤细胞中Ro60调控p53的分子机制，揭示Ro60-p53信号途径在肿瘤免疫和肿瘤增殖、放化疗敏感性调控中的功能机制，探讨该信号途径异常与肿瘤易感之间的分子关联及医学意义，为SLE及相关肿瘤患者的早期预警、治疗提供新的理论指导。

系统性红斑狼疮（systemic lupus erythematosus, SLE）是一种累及多器官、多系统的自身免疫性疾病，患者肿瘤发病率增高。自身抗原Ro60是SLE患者免疫反应的主要靶分子之一，但该分子的具体功能机制尚待研究揭示。本项目检测了多种组织来源的肿瘤细胞中RNA结合蛋白Ro60的表达情况及Ro60在肺癌细胞增殖、迁移、浸润及辐射敏感性调控中的作用。肿瘤组织芯片检测不同类型的肿瘤及其对应癌旁组织中Ro60的表达情况发现多种肿瘤组织中自身抗原Ro60的蛋白表达较癌旁组织异常增高或发生亚细胞分布改变，并存在组织特异性。肺癌、直肠癌、乳腺癌、胰腺癌等肿瘤组织中的Ro60胞浆和/或胞核表达异常增高；食管癌、结肠癌肿瘤组织中Ro60的胞浆/胞核分布比例出现异常，胞浆中的Ro60蛋白显著增加；胃癌、肝脏癌、肾癌等肿瘤组织中Ro60的表达与癌旁对照无显著差异。免疫组化检测了34例肺癌临床样本中Ro60和p53的表达情况，证实肺癌临床样本中Ro60在肿瘤组织细胞中的表达显著高于癌旁组织细胞。进一步的分子机制研究发现敲低表达Ro60使得A549、H460、801C、801D等多种肺癌细胞增殖减缓；细胞迁移能力和浸润能力减弱；并能够增进γ辐射引发的肿瘤细胞增殖抑制效应。敲底表达Ro60的A549细胞中p53的mRNA水平降低；对比敲低表达Ro60的A549（p53WT）细胞和的H1299（p53null）细胞的增殖和迁移能力证实该过程部分依赖于p53信号途径。综上，本项目研究首次发现多种肿瘤组织细胞中的Ro60蛋白异常高表达或出现亚细胞分布异常，Ro60参与调控肿瘤细胞的恶性增殖、迁移、浸润及放疗敏感性。上述研究结果为SLE及相关肿瘤易感个体的筛查、治疗提供了实验数据和理论指导，提示自身抗原Ro60有可能成为新的肿瘤监测指标及治疗靶点。