microRNA-26a介导肝癌细胞与肿瘤相关巨噬细胞之间的相互对话

There're inadequate drug therapies for hepatocellular carcinoma. The study of the cell biology of the hepatoma cells could help to develop of new therapies. In our previous study, we found that low expression of microRNA-26a (miR-26a) was associated with abnormal activation of the inflammatory factors, e.g. NF-κB and IL-6; and peritumoral infiltration of macrophages was associated with tumor invasion and metastasis; both low expression of miR-26a and macrophages infiltration were associated with poor prognosis after surgery. As macrophages were the main entities in which NF-κB/IL-6 pathway was activated, we hypothesized that hepatoma cells and macrophages may be linked via miR-26a. In our preliminary experiments, reduced expression of miR-26a in hepatoma cells enhanced the recruitment of macrophages and induced the macrophages to polarize into tumor-promoting M2 phenotype; inversely, macrophages could down-regulate the expression of miR-26a in hepatoma cells. We hypothesized that there's a cross talk between hepatoma cells and macrophages, and miR-26a may plays a crucial role in this cross talk. In this proposal, we will verify this hypothesis and study the molecular mechanisms of this cross talk. We planned to find the key transcription factor regulating miR-26a expression and the find the key target genes of miR-26a using protein microarray, ChIP assays and etc. By sort for the crucial factors in the cross talk, this study may provide new clues in the development of drug therapies for hepatocellular carcinoma.

肝癌的药物治疗严重缺乏，研究肝癌的生物学特性有助于发展新的治疗策略。我课题组的前期研究发现：肿瘤细胞内microRNA-26a（miR-26a）低表达与NF-κB、IL-6等炎症因子激活相关；癌周巨噬细胞浸润与肝癌侵袭转移相关；两者均为预后不良的标志。因巨噬细胞为NF-κB/IL-6炎症通路激活的主体，肝癌细胞与巨噬细胞间可能通过miR-26a相互联系。预实验中：肝癌细胞miR-26a表达降低可促进巨噬细胞募集并出现促肿瘤的M2表型；巨噬细胞反过来可抑制肝癌细胞miR-26a表达，两者间形成正反馈循环。我们推测，miR-26a在两种细胞的相互对话（cross talk）中处于核心地位。我们拟借助蛋白芯片和ChIP等技术，验证该假说并研究相互对话的机制，寻找调控miR-26a表达的关键转录因子及受miR-26a调控的下游关键靶基因，寻求潜在可干预的靶点以打破相互对话，为药物治疗提供新思路。

在肝癌的药物治疗领域，新的治疗严重缺乏，研究肝癌的生物学特征有助于发现新的治疗策略。我课题组的前期研究发现，肝癌细胞内microRNA-26a（miR-26a）低表达与NF-κB、IL-6等炎症因子激活相关；癌周巨噬细胞浸润与肝癌侵袭相关；两者均为肝癌患者预后不良的标志。在本项目开展过程中，我们发现miR-26a介导了肝癌细胞与巨噬细胞之间的相互对话，miR-26a通过抑制PI3K/AKT通路抑制肝癌细胞的巨噬细胞刺激因子（CSF-1）的表达，从而减少巨噬细胞在肿瘤微环境内的浸润；CSF-1通过与巨噬细胞表面的CSF1受体结合，从而激活MEK1/2-Erk1/2-c-Jun通路上调AIF的表达，使巨噬细胞出现促进肿瘤进展的M2表型。此外，我们还发现，在肝癌细胞内，miR-26a通过抑制EZH2分子，抑制肝癌细胞自身的上皮间质化转换。也就是说，miR-26a通过两种不同的机制抑制肝癌细胞侵袭转移。以这些发现为主要研究结果，已发表标注受本项目资助的SCI论文9篇，项目负责人为其中8篇为通讯作者，1篇为共同通讯作者。针对该通路的干预存在潜在的临床应用价值。临床前研究发现，使用CSF-1受体的拮抗剂PLX3397可以逆转巨噬细胞的M2极化状态从而抑制肝癌生长。