HnRNP A1通过调控炎-靶细胞相互作用促进慢性结肠炎恶性转化的分子机制

Previous studies show that hnRNP A1 is positively related to the incidence of Crohn''s disease and colon cancer, and the knock-down of hnRNP A1 results in inactivation of NF-κB and STAT3, suggesting the malignant transformation of chronic colitis can be exacerbated by hnRNP A1. In the present study, the expression of hnRNP A1 was further compared in different tissues from chronic colitis and colon cancer and the relationships between hnRNP A1 and the key inflammation-cancer molecules such as NF-κB and STAT3 were examined. Then, the conditional knockout mice of hnRNP A1 in inflammatory cells (macrophages) and target cells (colonic epithelial cells) were established and the roles of hnRNP A1 on the experimental colitis-related colon cancer model as well as the interaction between macrophages and colonic epithelial cells were explored. Furthermore, the molecular mechanisms of the activation of macrophage, the excessive proliferation, anti-apoptosis and carcinogenesis of colonic epithelial cells as well as the regulation of NF-κB and STAT3 pathways by hnRNP A1 were investigated. Finally, the effect of targeted intervention of hnRNP A1 in the experimental colitis-related colon cancer model was also examined. This study provides a theoretical basis for targeted therapy of inflammation-associated tumors.

前期研究表明，核不均一核糖核蛋白A1（hnRNP A1，以下称A1）与慢性结肠炎及结肠癌患者的发病呈正相关，且敲低A1可下调炎-癌信号分子NF-κB, STAT3的活化，提示A1很可能促进慢性结肠炎的恶性转化。本项目拟进一步比较A1在慢性结肠炎和结肠癌不同组织中的表达差异，确认其与NF-κB, STAT3等分子的相关性；分别建立A1在巨噬细胞和结肠上皮细胞中的条件性敲除小鼠，诱发实验性结肠炎-癌模型，与野生型小鼠相比较，探讨炎、靶细胞中A1介导的信号转导网络及其与疾病进展指标的关联，从中提炼出A1作为炎-靶细胞实现相互作用的共性效应分子的特征，阐明其影响巨噬细胞活化、促进结肠上皮细胞过度增殖进而癌变的信号通路，确证A1具有调控NF-κB和STAT3这两条炎-癌相关通路的节点样功能；在此基础上考察靶向干预A1对实验性结肠炎-癌模型的抑制作用，为靶向治疗炎症相关肿瘤提供理论依据。

HnRNP A1是一类广谱表达的RNA 结合蛋白，虽然已有报道hnRNP A1 在炎症性疾病以及肿瘤的发生发展中扮演着重要角色，但其在慢性结肠炎恶性转化中的功能尚不明确。我们收集了结肠癌患者正常、癌旁及结肠癌组织共199 例，进行hnRNP A1 蛋白表达的免疫组化检测，发现与正常、癌旁组织相比，hnRNP A1 表达水平在结肠癌组织中呈显著上升趋势。同时，我们也发现在慢性结肠炎病人活检标本中，hnRNP A1表达水平也明显高于正常结肠组织。在结肠癌细胞株HCT-116上稳定敲低hnRNP A1，NF-κB和STAT3的活化水平明显下调，提示hnRNP A1正调控NF-κB和STAT3通路。进一步，肠上皮细胞中hnRNP A1敲除导致小鼠急性DSS结肠炎得到明显缓解，结肠组织NF-κB和STAT3的活化水平亦明显下调，同时在AOM-DSS 经典炎-癌转化模型中，我们也发现小鼠肠上皮细胞缺失hnRNP A1使得肿瘤生成减少，但在肿瘤细胞系中的试验却证实hnRNP A1的敲低并未影响肿瘤细胞的增殖和凋亡。为了阐明肠上皮细胞缺失hnRNP A1 导致结肠炎减轻、肿瘤减少的详细机制，我们通过GST-hnRNP A1 pull-down实验，找到hnRNP A1的一个新结合蛋白MAT1A，并且发现hnRNP A1的缺失影响了MAT1A的功能，从而导致了上皮细胞抑制机体免疫功能的关键分子PD-L1的表达显著升高。同时，基于上述基础研究发现了能通过与hnRNP A1 特异性结合改善慢性结肠炎恶性转化的小分子化合物S5，验证了靶向干预hnRNP A1 在实验性结肠炎-癌转化模型中的抑制作用，为hnRNP A1 作为慢性结肠炎恶性转化潜在治疗靶标提供理论依据。我们的研究阐明了hnRNP A1 对肠上皮细胞的功能调控及其对炎症及肿瘤转化过程的影响，并进一步探讨了其调控机理，为炎症相关肿瘤的治疗提供新的理论依据和干预手段。此外，我们还发现了一系列新型调控炎症和癌症的化合物，为炎-癌基础研究的转化应用打下基础，并通过发现穿心莲内酯诱导自噬抑制炎症小体的新机制，为基于炎癌转化过程的干预实现从抗炎到抗癌提供了新的治疗策略。本项目共发表标注91229109资助的SCI论文9篇，其中6篇发表在影响因子大于5 的刊物上，2篇发表在影响因子大于10 的刊物上。