Mitochondrial fission-induced mtDNA stress promotes tumor-associated macrophage infiltration and HCC progression
Mitochondrial fission-induced mtDNA stress promotes tumor-associated macrophage infiltration and HCC progression
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DOI：
10.1038/s41388-019-0772-z
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发表时间：
2019-06-20
期刊：
影响因子：
8
通讯作者：
Xing, Jinliang
中科院分区：
文献类型：
--
作者：
Bao, Dengke;Zhao, Jing;Xing, Jinliang
肿瘤相关巨噬细胞(TAM)参与了肝细胞癌的进展。然而，TAMs渗透到肝细胞癌微环境的分子机制还很不清楚。最近的研究报道，线粒体类核结构的改变会诱导线粒体DNA(MtDNA)释放到胞浆中，这被认为是mtDNA应激，从而调节先天免疫。在此，我们旨在探讨线粒体分裂是否诱导线粒体DNA应激，进而促进的浸润和肝癌的进展。采用激光共聚焦显微镜和实时荧光定量聚合酶链式反应检测肝癌细胞胞浆线粒体DNA含量。应用免疫组织化学方法研究肝细胞癌组织中线粒体分裂关键调节蛋白--动力蛋白相关蛋白1(Drp1)的表达与CD163(TAMS标志物)阳性细胞百分率的关系。最后，研究了肝癌细胞中Drp1过表达对TAMs募集和极化的影响。我们的数据显示，Drp1的表达增加与TAMs在肝细胞癌组织中的渗透呈正相关。DRP1介导的线粒体分裂通过TLR9介导的NF-kappaB信号通路诱导胞浆mtDNA应激促进肝癌细胞分泌CCL2，从而促进的募集和极化。用DNase I耗尽胞浆mtDNA，或用TLR9拮抗剂阻断TLR9通路，在DRp1过表达的肝癌细胞中，TLR9或p65的siRNA显著降低TAMS的募集和极化。拮抗剂阻断CCR2可明显减少的侵袭，抑制小鼠肝细胞癌的发展。综上所述，我们的研究结果揭示了一种新的机制，即线粒体裂变诱导的线粒体DNA应激导致在肝细胞癌中的浸润。
Tumor-associated macrophages (TAMs) contribute to hepatocellular carcinoma (HCC) progression. However, the molecular mechanism underlying the infiltration of TAMs into HCC microenvironment is largely unclear. Recent studies have reported that alteration of mitochondrial nucleoid structures induces mitochondrial DNA (mtDNA) release into the cytosol, which is recognized as mtDNA stress, and consequently regulates innate immunity. Here we aimed to investigate whether mitochondrial fission induces mtDNA stress and then promotes TAM infiltration and HCC progression. Confocal microscopy and real-time PCR were used to detect cytosolic mtDNA content in HCC cells. The relationship between the expression of mitochondrial fission key regulator dynamin-related protein 1 (Drp1) and the percentage of CD163 (a marker of TAMs)-positive cells was investigated in HCC tissues using immunohistochemistry. Finally, the effect of Drp1 overexpression in HCC cells on recruitment and polarization of TAMs was investigated. Our data showed that increased Drp1 expression was positively correlated with the infiltration of TAMs into HCC tissues. Drp1-mediated mitochondrial fission induced the cytosolic mtDNA stress to enhance the CCL2 secretion from HCC cells by TLR9-mediated NF-kappa B signaling pathway, and thus promoted the TAM recruitment and polarization. Depleting cytosolic mtDNA using DNase I or blocking TLR9 pathway by TLR9 antagonist, siRNA for TLR9 or p65 in HCC cells with Drp1 overexpression significantly decreased the recruitment and polarization of TAMs. Blocking CCR2 by antagonist significantly reduced TAM infiltration and suppressed HCC progression in mouse model. In conclusion, our findings reveal a novel mechanism of TAM infiltration in HCC by mitochondrial fission-induced mtDNA stress.