CUEDC2在炎性肠病及肠炎相关肠癌发生中的作用和机制研究

Colorectal cancer is a frequent malignant tumor and the 4th most common cause of cancer mortality worldwide. The morbidity of CRC in China keeps increasing. It is widely believed that inflammatory bowel disease is one of the major causes of colorectal cancer. However, the molecular mechanisms by which inflammation promotes cancer development are still being uncovered. We have illustrated a new mechanism governing macrophage-mediated inflammatory response (Nature Immunology 2010). On the basis of our previous study on inflammation induced cancer, we have found that as a regulator of macrophage function, CUEDC2 is highly expressed in colorectal cancer and deficiency of CUEDC2 led to increased susceptibility of DSS-induced colitis. Moreover, in a previous research project of regulation of macrophage function by CUEDC2 [grant#: 31270934], we identified that miR-324-5p modulated expression of CUEDC2 is an important molecular evens in regulating of macrophage activation. Together, we hypothesized that the increased susceptibility to colitis and CAC of cuedc2 knock-out mice is most likely due to the dysfunction of macrophages lacking CUEDC2. To test this hypothesis, we will firstly evaluate the effect of CUEDC2 on the development of colitis and CAC with CUEDC2-deficient mice; to explore the contribution of dysfunction of macrophage lacking CUEDC2 to the developing of colitis and CAC by conditional knock-out mice in association with bone marrow and macrophage transfer; also to reveal the involvement of CUEDC2 in the inflammation induced colon cancer process by analyzing the expression of CUEDC2 and its targeting microRNA, miR-324-5p, during the development of colitis and CAC, in both mouse model and patient samples. This research will elucidate the mechanistic role of CUEDC2 in the process of development of colitis-associated cancer; make it possible to design new therapeutic strategies to treat CAC based on CUEDC2 and provide new insights to inflammation induced cancers.

炎性肠病作为诱发结直肠癌的重要原因之一，其机制一直是国际前沿领域的热点问题。我们前期研究揭示了巨噬细胞介导炎症反应的新机制（Nature Immunology，2010，第一作者），近期又发现CUEDC2调节巨噬细胞功能，并在结直肠癌中高表达，而且该基因敲除小鼠对肠炎高度易感。基于以上线索，本项目将深入研究CUEDC2在肠炎诱发肠癌过程中的作用及机制。主要策略是利用我室已构建的CUEDC2敲除小鼠建立肠炎及其相关肠癌研究模型，评价CUEDC2在肠炎到肠癌过程中的作用；通过髓系条件敲除和骨髓及巨噬细胞移植等手段，明确CUEDC2是否通过调控巨噬细胞功能影响肠炎及其相关肠癌的发生；结合临床炎性肠病和肠癌病人样本分析，挖掘CUEDC2与疾病进程和预后的相关关系。上述努力将阐明CUEDC2影响肠炎及其相关肠癌发生的作用机制，并可能发现干预肠炎相关肠癌的新靶点，为炎症诱发肿瘤的治疗研究提供重要线索。

前期研究中我们发现CUEDC2调节巨噬细胞功能，并在结直肠癌中高表达，而且该基因敲除小鼠对肠炎高度易感。在后期研究中我们明确CUEDC2在巨噬细胞分化过程中显著上调（人以及小鼠样品）。证明CUEDC2的缺失不影响巨噬细胞的分化。证实该基因的缺失不影响巨噬细胞吞噬能力。但是该基因缺失导致巨噬细胞炎症因子分泌过度，该基因的缺失会促进巨噬细胞M1极化而对M2极化没有影响，我们发现CUEDC2通过调节巨噬细胞中NF-kB信号通路的强度，调节巨噬细胞的炎症反应。同时，还发现CUEDC2基因敲除小鼠对实验性结直肠炎高度敏感，体重下降显著，结肠明显缩短，腹泻及直肠出血症状严重，组织学评价也明显高于野生型小鼠。通过给野生型小鼠进行巨噬细胞移植后诱导肠炎，证实野生型小鼠实验组由于获得了CUEDC2表达缺失的巨噬细胞而对实验性结直肠炎敏感，证明了CUEDC2能够通过对巨噬细胞功能的调节而影响肠炎的发生。我们也同时建立DSS与AOM联合用药诱导炎性相关肿瘤模型，在前期发现的基础上探索了CUEDC2对于结直肠癌发生发展的影响，结果显示，CUEDC2缺失的小鼠对化学诱导的结肠癌模型也高度敏感，荷瘤量显著高于野生型小鼠。进一步，收集临床结直肠癌患者样本进行CUEDC2以及巨噬细胞标志物CD68的免疫组化染色，发现CUEDC2在肿瘤相关巨噬细胞中表达水平相对于癌旁组织显著低，同时我们分离患者的癌及癌旁组织浸润的巨噬细胞进行检测，发现microRNA-324-5p的表达丰度与CUEDC2显著负相关。深入研究发现IL-4在结直肠癌患者肿瘤组织中高表达，并促进巨噬细胞中microRNA-324-5p的水平从而下调肿瘤相关巨噬细胞中CUEDC2的表达水平。.我们的研究发现巨噬细胞分化过程中miRNA-324-5p对CUEDC2表达的调控是防止不适当炎症反应发生的关键机制，miR-324-5p-CUEDC2轴在巨噬细胞中的失衡与结肠癌密切相关，研究结果为结直肠癌的治疗提供了潜在的新靶点。