APC基因突变背景下结肠腺瘤癌变的炎症信号网络研究及调控机制

In this study, we aim to investigate the molecular mechanisms of intestinal adenoma and colorectal cancer (CRC). Many studies showed that the mutation of APC gene, adenomatous polyposis coli (APC), would affect the signal pathway of Wnt-β-catenin. Using the new models of intestinal cancer with double specific targets, including the mice models of APCMin+/Fas deficiency, APCMin+/COX transgenes and APCMin+/Vegfr2-KI(knock in), we investigate the mechanisms of the interaction of APC mutation and dysregulation of the Wnt signaling pathway in the intestinal adenomas. We hypothesize that APC mutation could induce the dysregulation of the Wnt-β-catenin and then resulted in a series of new related signaling pathways in the development of colorectal cancer from intestinal adenoma in the background of APC mutation. The growth and invasion of intestinal adenomas are increased exposure to inflammatory stress. Based on these expectations, we hypothesize the following new signaling pathways. (1) The formation and development of intestinal adenoma are associated with the activation of NF-κB-COX-2/PGE2-MMP-7-Fas/CD95 in intestinal adenomas. (2) The development of CRC from intestinal adenoma might due to the involvement of activation of protein from PPAR family. (3) The invasion and metastasis of colorectal cancer cells might be due to increase of activity of Ras-Raf(MAP KKK)-MAPK/ERK1/2-MMPs. (4) The stimulation of signaling pathway COX-2/PGE2-KDR-Shb-PI3K-AKT or KDR-PLC-γ-PKC-Raf-MEK-MAPK might increase the formation of EMT and angiogenesis in the tissues of colorectal cancers. These studies will find the new way of investigation in the regimen in chemoprevention against intestinal tumorigenesis.

APC突变可能致Wnt-β-catenin异常传导，并与参入的炎症信号相互影响形成新的网络通路。我们拟以APCMin+背景建立的APCMin+/Fas deficiency，APCMin+/COX transgenes和APCMin+/Vegfr2-KI(knock in)肠癌小鼠模型，研究APC背景下如何影响Wnt-异常传导，产生新炎症信号传递网络过程。假设这些新模型的肠微腺瘤形成与癌变过程中存在以下信号网络：①炎症信号循NF-κB-COX-2/PGE2-MMP-7-Fas/CD95异常传导介导肠腺瘤增殖、凋亡抵抗；②炎症因子对PPAR家族网络信号激活可能介导肠微腺瘤恶变和增殖作用；③炎症对Ras-Raf(MAP KKK)-MAPK/ERK1/2-MMPs激活可能传递浸润转移信号；④COX-2/PGE2-KDR-Shb-PI3K-AKT的异常传导可能促进微血管形成和肠上皮-间质化EMT。

结肠癌(CRC)发生机制复杂，多数病人与APC基因突变，激活Wnt-β –catenin信号传导有关。Wnt-β –catenin信号异常传导会导致细胞恶变和癌的发生。然而，肿瘤炎症微环境的形成对于结肠癌的发病也起到至关重要的作用，加速炎癌转化过程。针对结肠癌炎癌转化过程及防治措施，本项目建立了多个以炎症靶点为特征的小鼠模型，包括ApcMin/+/IFN-γ+/-肠癌小鼠，APCMin+/COX，ApcMin/+/ATG5+/-，ApcMin/+/Sphk2++，ApcMin/+/IGF1-R+/-等小鼠模型，针对这些模型进行了如下方面的研究：（1）干扰素-γ(IFN-γ)缺陷对APC突变背景的肠炎癌转化影响，发现IFN-γ在炎癌转化过程中起到限速因子作用，IFN-γ缺陷加速结肠癌炎癌转化过程；（2）研究自噬相关基因ATG5缺陷对ApcMin/+ATG5+/-小鼠肠腺瘤癌变的影响，发现ATG5缺陷促进了APC基因突变介导的肠道肿瘤发生，ATG5缺失能激活ApcMin/+小鼠肠道的Wnt/β-catenin信号通路，其机制可能也与对EGFR/ERK1/2信号通路的活化作用有关。然而，ATG5缺陷却能提高干扰素-γ对ApcMin/+小鼠肠肿瘤的抑制作用；（3）研究了CXCR4/CXCL12轴激活通过PI3K/AKT/ mTOR和MAPK/ERK信号通路作用，CXCR4/CXCL12轴激活促进β–catenin核转位，进而促进下游靶基因MMP-7、CyclinD1和Survivin等，促进炎癌转化与增殖。（4）鞘氨醇激酶2(SphK2)对全反式维甲酸(ATRA)活性的影响及促进结肠炎癌转化研究，高表达SphK2明显刺激炎症因子表达，促进炎癌转化；（5）研究IGF-1R(type I insulin-like growth factor receptor)在炎癌转化中作用，发现敲出IGF-1R细胞和小鼠炎症信号表达下调，抑制炎癌转化。（6）Riccardin D对APCMin+小鼠肠微腺瘤炎癌转化有抑制作用。（7）乳香酸具有很强抑制APCMin+小鼠肠微腺瘤炎癌转化作用。