CpG on carbon nanotubes inhibits migration of brain tumor cells while activating immune cells

Even when treated with aggressive current therapies, patients with glioblastoma usually survive less than two years and exhibit a high rate of recurrence. CpG is an oligonucleotide that activates the innate immune system via TLR9 activation. Injection of CpG into glioblastoma tumors showed promise as an immunotherapy in mouse models but proved disappointing in human trials. One aspect of glioma that is not addressed by CpG therapy alone is the highly invasive nature of glioma cells, which is associated with resistance to radiation and chemotherapy. Here, we demonstrate that single-walled carbon nanotubes non-covalently functionalized with CpG (SWNT/CpG) not only retain the immunostimulatory property of the CpG, but interestingly also inhibit the migration of glioma cells without affecting cell viability or proliferation. SWNT/CpG activated macrophages by induction of the TLR9/NF-κB pathway, but actually decreased NF-κB activation in glioma cells. By using RNA-seq to compare the effect of SWNT/CpG treatment on glioma cells and macrophages, we confirmed that SWNT/CpG treatment has cell type-specific effects on gene expression. Through RNA-seq analysis, we identified a number of differentially affected pathways which may be involved in glioma cell migration inhibition and observed reduced gene expression in DNA repair pathways for SWNT/CpG-treated glioma cells. The migration inhibition of glioma cells was correlated with reduced intracellular levels of reactive oxygen species (ROS), suggesting that an antioxidant-based mechanism mediates the observed effects. To our knowledge, SWNT/CpG is the first therapy that inhibits the migration of cancer cells while stimulating the immune system.

胶质母细胞瘤（glioblastoma）患者即便接受现行的积极治疗，生存期通常也不足两年，且复发率居高不下。CpG寡核苷酸（CpG oligonucleotide）是一类通过激活TLR9（Toll样受体9）来触发先天免疫系统应答的寡核苷酸。将CpG注射至胶质母细胞瘤瘤体内的免疫疗法，在小鼠模型中展现出应用前景，但在人体临床试验中效果却不尽如人意。单一CpG疗法未能解决胶质瘤（glioma）的一个关键特性：胶质瘤细胞的高侵袭性，而该特性与肿瘤对放疗及化疗的耐药性密切相关。本研究证实，经CpG非共价功能化修饰的单壁碳纳米管（SWNT/CpG）不仅保留了CpG的免疫刺激活性，还能在不影响细胞活力与增殖能力的前提下，有效抑制胶质瘤细胞的迁移。SWNT/CpG可通过诱导TLR9/NF-κB（核因子κB）通路激活巨噬细胞，但在胶质瘤细胞中却会下调NF-κB的激活水平。研究人员通过RNA测序（RNA-seq）对比SWNT/CpG处理对胶质瘤细胞与巨噬细胞的影响，证实该制剂对基因表达的调控具有细胞类型特异性。通过RNA-seq分析，我们鉴定出多条可能参与胶质瘤细胞迁移抑制的差异调控通路，同时观察到经SWNT/CpG处理的胶质瘤细胞中，DNA修复通路的基因表达水平显著降低。胶质瘤细胞的迁移抑制效应与细胞内活性氧（reactive oxygen species, ROS）水平降低呈相关性，这提示抗氧化机制介导了本次观测到的生物学效应。据我们所知，SWNT/CpG是首款兼具抑制癌细胞迁移与激活免疫系统双重功能的治疗方案。