环二鸟苷酸（c-di-GMP）信号系统激活p53及其抗肿瘤功能研究

As the most essential tumor suppressor, TP53 is mutated in approximately 50% of human malignancies. In most cancers lacking mutation, wild-type p53 is inactivated by oncoproteins. Because of its near universal alteration in cancer, p53 or its pathway has been an attractive target to develop a new type of molecule targeting anticancer therapy. As a defense mechanism, when infected with retroviruses or cytosolic DNA, mammalian cells assemble endogenous cyclic dinucleotides (CDN) which is recognized by the intracellular protein STING to induce type I.interferon (IFN) responses. Cyclic di-GMP (c-di-GMP) has been recently reported to be a new class of adjuvant against cancer, however, the precise underlying mechanisms remains unknown. Since it could be synthesized by the human body, it might be safer than traditional chemotherapy drugs with fewer side effects.Due to the unique characteristics of c-di-GMP, we hypothesize that c-di-GMP could be applied to cancer therapy in clinic as a p53 activator. We plans to use various cells and animal models to verify the activate effect of c-di-GMP on p53 in details, to explore the anti-tumor growth and metastasis ability and the activity to sensitize chemotherapeutic agents. Our preliminary data demonstrated that c-di-GMP remarkably induce p53 expression, triggered cancer cell apoptosis and inhibited cell metastasis. Carrying out of this project provide significant molecular basis of cyclic dinucleotides in clinical settings for cancer therapy.

TP53是最重要的抑癌基因，在约50%的人类肿瘤中存在突变，且在具野生型TP53肿瘤中，p53蛋白活性被癌蛋白显著抑制，因此迫切需要有效的新型p53靶向药物用于肿瘤的治疗。外源性DNA或病原体入侵会使人体产生环二核苷酸。环二核苷酸通过激活干扰素基因表达来强化人体的先天免疫体统。最近有研究报道，环二鸟苷酸（c-di-GMP）可作为免疫佐剂用于肿瘤治疗，但其作用机制尚不明确。鉴于c-di-GMP的生物学特性，我们推测 c-di-GMP是否可以通过激活p53而发挥抗肿瘤活性。本项目将首次利用多种细胞和动物模型细致研究 c-di-GMP对p53的激活作用及方式并探究其抗肿瘤生长、转移及增敏化疗药物的活性。项目前期数据显示c-di-GMP可显著激活p53的表达，并表现出对肿瘤细胞凋亡诱导和抑制迁移的活性。本项目的开展为环二核苷酸类药物在肿瘤治疗中的应用提供有力的理论支撑。

TP53是最重要的抑癌基因，在约50%的人类肿瘤中存在突变，P53的功能主要反映在对外界压力的应答，作为重要的转录因子，通过转录下游众多的靶基因使机体对相应的压力做出适当的反应，如DNA损伤和其它的细胞内压力、代谢压力包括低氧、癌基因激活及营养缺乏等压力被细胞感应后激活p53，活化的p53通过促进细胞周期阻滞、调节DNA修复、抑制细胞转移、诱导细胞衰老、凋亡、自噬、调节细胞代谢等来抑制细胞向恶性肿瘤的转化。在具野生型TP53肿瘤中，p53蛋白活性被癌蛋白显著抑制，因此迫切需要有效的新型p53靶向药物用于肿瘤的治疗。外源性DNA或病原体入侵会使人体产生环二核苷酸。环二核苷酸通过激活干扰素基因表达来强化人体的先天免疫体统。最近研究报道，环二鸟苷酸（c-di-GMP）可作为免疫佐剂用于肿瘤治疗，但作用机制尚不明确。我们研究发现c-di-GMP对野生型p53及其下游效应因子（CDKN1A、MDM2、PUMA、BAX）存在激活作用。同时，发现了c-di-GMP对多类肿瘤细胞转移的抑制作用。应用RNA-seq测序分析，我们在分子水平上阐明了其抑制转移的机制是通过上调一种MicroRNA（单链非编码小分子RNA，miRNA）——MiR4489而实现的。同时我们采用动物模型确证了c-di-GMP在体内良好的抗肿瘤转移效果，揭示了c-di-GMP在治疗实体肿瘤中的新用途。本项目开展为该类结构新型的、安全经济的环二核苷酸类药物在p53的肿瘤靶向治疗及肿瘤转移中的可能应用提供有力的理论支撑，为肿瘤的有效治疗指示新的方向。