Prophylactic TLR9 stimulation reduces brain metastasis through microglia activation
Prophylactic TLR9 stimulation reduces brain metastasis through microglia activation
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DOI：
10.1371/journal.pbio.2006859
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发表时间：
2019-03-01
期刊：
影响因子：
9.8
通讯作者：
Blinder, Pablo
中科院分区：
文献类型：
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作者：
Benbenishty, Amit;Gadrich, Meital;Blinder, Pablo
脑转移在各种类型的癌症中很常见，鉴于现有治疗方法的低疗效，脑转移通常是晚期的。因此，预防它们具有最大的临床意义，而预防性治疗可能是最有效的策略。在这里，我们表明系统性预防性给予Toll样受体(TLR)9激动剂CpG-C对脑转移瘤是有效的。在三种小鼠肿瘤模型中，急性和长期全身应用CpG-C可减少肿瘤细胞在脑内的种植和生长，包括人和小鼠肺癌转移和自发性黑色素瘤来源的脑转移。在研究CpG-C治疗作用的机制时，我们发现，在大脑中，与外围不同，自然杀伤(NK)细胞和单核细胞不参与控制转移。接下来，我们证明了系统给药的CpG-C被内皮细胞、星形胶质细胞和小胶质细胞摄取，而不影响血脑屏障(BBB)的完整性和肿瘤脑外渗。体外试验表明，小胶质细胞，而不是星形胶质细胞，是CpG-C作用的媒介，通过小胶质细胞与肿瘤的直接接触，增加肿瘤杀伤和吞噬作用。在体内，CpG-C激活的小胶质细胞显示出凋亡诱导和吞噬相关基因的mRNA表达水平升高。活体成像显示，在肿瘤脑侵袭的早期阶段，CpG-C激活的小胶质细胞比未激活的小胶质细胞更多地接触、杀伤和吞噬肿瘤细胞。用米诺环素阻断体内小胶质细胞的激活，用集落刺激因子1抑制剂阻断小胶质细胞的耗竭，表明小胶质细胞介导了CpG-C的抗肿瘤作用。总体而言，结果提示预防性CpG-C治疗是一种新的脑转移干预措施，通过激活小胶质细胞。作者总结：脑转移瘤很常见，而且往往是晚期的。因此，减少癌症的发生可以显著改善癌症的预后。在实验和自发性脑转移模型中，系统预防性和围手术期给予TLR9激动剂CpG-C可以减少转移生长，使用小鼠和人类肿瘤。Cpg-C在脑内被摄取，不影响血脑屏障的完整性和肿瘤的渗出。体外检测、流式细胞仪成像和活体成像表明，小胶质细胞通过接触性肿瘤杀伤和吞噬作用调节CpG-C效应，这与体内的mRNA谱相一致。体内耗竭研究证明，小胶质细胞，而不是NK细胞或单核细胞，介导了CpG-C的有益作用，也通过阻止小胶质细胞的激活而受到阻碍。总之，围术期应用CpG-C治疗应被认为是临床相关的。
Brain metastases are prevalent in various types of cancer and are often terminal, given the low efficacy of available therapies. Therefore, preventing them is of utmost clinical relevance, and prophylactic treatments are perhaps the most efficient strategy. Here, we show that systemic prophylactic administration of a toll-like receptor (TLR) 9 agonist, CpG-C, is effective against brain metastases. Acute and chronic systemic administration of CpG-C reduced tumor cell seeding and growth in the brain in three tumor models in mice, including metastasis of human and mouse lung cancer, and spontaneous melanoma-derived brain metastasis. Studying mechanisms underlying the therapeutic effects of CpG-C, we found that in the brain, unlike in the periphery, natural killer (NK) cells and monocytes are not involved in controlling metastasis. Next, we demonstrated that the systemically administered CpG-C is taken up by endothelial cells, astrocytes, and microglia, without affecting blood-brain barrier (BBB) integrity and tumor brain extravasation. In vitro assays pointed to microglia, but not astrocytes, as mediators of CpG- C effects through increased tumor killing and phagocytosis, mediated by direct microglia-tumor contact. In vivo, CpG-C-activated microglia displayed elevated mRNA expression levels of apoptosis-inducing and phagocytosis-related genes. Intravital imaging showed that CpG-C-activated microglia cells contact, kill, and phagocytize tumor cells in the early stages of tumor brain invasion more than nonactivated microglia. Blocking in vivo activation of microglia with minocycline, and depletion of microglia with a colony-stimulating factor 1 inhibitor, indicated that microglia mediate the antitumor effects of CpG-C. Overall, the results suggest prophylactic CpG-C treatment as a new intervention against brain metastasis, through an essential activation of microglia.Author summary Brain metastases are prevalent and often terminal. Thus, reducing their occurrence could markedly improve cancer outcome. We show that systemic prophylactic and perioperative administration of a TLR9 agonist, CpG-C, reduced metastatic growth in experimental and spontaneous brain metastasis models, employing mouse and human tumors. CpG-C was taken up in the brain without affecting blood-brain barrier integrity and tumor extravasation. In vitro assays, imaging flow cytometry, and intravital imaging pointed to microglia as mediators of CpG-C effects through contact-dependent tumor killing and phagocytosis, corresponding with in vivo mRNA profile. In vivo depletion studies proved that microglia, but not NK cells or monocytes, mediated the beneficial effects of CpG-C, also hindered by blocking microglial activation. In toto, perioperative treatment with CpG-C should be considered clinically relevant.