NEIL3对肝癌微环境中巨噬细胞功能的调控及机制研究

Hepatocellular carcinoma (HCC) usually develops within an environment of chronic inflammation. Macrophages in the inflammatory tumor microenvironment play an important role in the development of HCC. So the study on regulating the function of tumor-associated macrophages in HCC is essential for antitumor immunity and immunotherapy. Previous studies indicated NEIL3, as a DNA damage repair factor, displays high expression in tumor cells and immune cells. The mutation of NEIL3 correlated with recurrent infection and B-cell dysfunction. However, the function of NEIL3 in tumor immunity and innate immune cells remains undiscovered. We analyzed the TCGA database and find the expression of NEIL3 increased in tumor samples of HCC patients, and the expression of NEIL3 negatively correlated with the survival time. We also confirmed that expression in the specimens we've collected. These results implied the function of NEIL3 in HCC. Then we discovered that after treated with HepG2 culture medium, the expression of NEIL3 increased in macrophage. Knocking-down of NEIL3 in macrophage results in the upregulation of inflammatory cytokines. Based on these results, we hypothesize that the tumor microenvironment upregulates the expression of NEIL3 in macrophage, which suppresses the antitumor activity of macrophage and promote the development of HCC. Our study aims to provide new perspective of tumor immunotherapy targeted on macrophages.

肝癌往往由长期的慢性肝炎发展而来，炎性微环境中的巨噬细胞在肝炎相关的肝癌中起到了重要作用，因此找寻调节肿瘤炎性微环境中巨噬细胞功能的分子靶点就对于抗肿瘤免疫有重要积极意义。以往研究表明，NEIL3作为一种DNA损伤修复相关分子，在肿瘤组织和免疫细胞中均有较高表达，并且与多发性感染和B细胞功能异常相关，但其在肿瘤免疫和天然免疫细胞中的作用尚不明确。我们查阅了TCGA数据库，发现NEIL3在肝细胞肝癌组织中表达明显升高，并且其表达与生存期呈负相关，我们随后在临床样本中也验证了这一发现；肿瘤细胞系培养上清刺激巨噬细胞后，NEIL3表达明显升高；敲低NEIL3后，巨噬细胞分泌的炎症因子明显上升。基于这些研究结果，我们初步推测肿瘤微环境导致了NEIL3上调，抑制了巨噬细胞的抗肿瘤免疫活性，促进了肿瘤的发生发展。本研究预期为靶向巨噬细胞的肿瘤免疫治疗提供新的理论依据。

以往研究表明，NEIL3作为一种DNA损伤修复相关分子，在肿瘤组织和免疫细胞中均有较高表达，并且与多发性感染和B细胞功能异常相关，但其在肝癌及肿瘤免疫中的作用尚不明确。通过本研究的执行，我们发现NEIL3在促进肝癌的发展中具有重要作用。首先通过对数据库的分析，我们发现NEIL3在肝癌临床样本中表达显著上调，并且与病人的生存期呈负相关。随后我们分别在THP-1来源的巨噬细胞和肝癌细胞系中研究NEIL3对其的调控功能。一方面，THP-1来源的巨噬细胞NEIL3敲低后，我们发现其表达的促炎因子下降，提示NEIL3可能通过抑制巨噬细胞的抗肿瘤活性促进肝癌的发展。另一方面，肿瘤细胞缺失NEIL3后，其增殖受到抑制，同时对索拉菲尼的敏感性增加，在小鼠模型中肿瘤生长减缓。在TCGA数据库中NEIL3的表达上调和干细胞功能相关通路呈正相关性，进一步机制研究显示，NEIL3缺失后，肝癌细胞的成球能力下降，干细胞相关基因特别是CD44的表达显著下调，证实NEIL3缺失抑制了肝癌细胞的干性，并且这种干性下调是通过下调了STAT3和Notch通路实现的。我们的研究为肝癌的诊断和治疗提供了新的理论依据和参考靶点，有助于靶向药物的研究。