Chronic compression recapitulates transcriptional, metabolic, and functional state changes in macrophages associated with pro-tumor phenotypes

Macrophages comprise a significant portion of the glioblastoma tumor microenvironment and are essential in promoting immunosuppression and tumor progression. Solid tumors such as glioblastoma generate solid stress as they expand, creating a compressive microenvironment for mechanosensitive immune cells including macrophages. Macrophages are known to respond to various mechanical stimuli but have not yet been studied in the context of chronic compression observed in growing tumors. Here, we used a custom in vitro compression system to elucidate the effects of compressive solid stress on murine macrophages. We found that macrophages have significant morphological, transcriptional, metabolic, and functional responses to compression. These changes corresponded to both canonical pro- and anti-inflammatory macrophage states. The gene expression signatures of compressed macrophages more closely resembled those of glioma-associated macrophages known to be associated with worse patient outcomes. These results indicate that compression alone, independent from tumor cell-derived biochemical factors, may contribute to the pathological tumor-associated macrophage phenotype. This could represent a vicious cycle of tumor immunomechanics and mechano-immunology. Targeting solid stress in tumors or the response to solid stress by macrophages may interrupt this feedback loop to help normalize the tumor immune microenvironment and improve glioblastoma response to immunotherapy. Overall design: RNA-seq profiling of RAW264.7 macrophages under 24 hours of statioc compressive solid stress (weighted) compared to uncompressed controls (agarose).

巨噬细胞（Macrophages）是胶质母细胞瘤肿瘤微环境的重要组成部分，在促进免疫抑制与推动肿瘤进展过程中发挥关键作用。诸如胶质母细胞瘤在内的实体瘤在增殖扩张时会产生实体应力，为包括巨噬细胞在内的机械敏感性免疫细胞营造出压迫性微环境。已知巨噬细胞可对多种机械刺激产生应答，但目前尚未有针对生长性肿瘤中存在的慢性压迫环境下巨噬细胞的相关研究。本研究采用定制化体外压迫系统，阐明实体压迫应力对小鼠巨噬细胞的调控效应。研究发现，巨噬细胞在受压后会出现显著的形态学、转录组学、代谢组学及功能层面的应答反应，这些变化同时对应经典的促炎与抗炎巨噬细胞极化状态。受压巨噬细胞的基因表达特征与已知的、与患者不良预后密切相关的胶质瘤相关巨噬细胞更为相似。上述结果表明，即便不依赖肿瘤细胞衍生的生化因子，单纯的压迫作用即可诱导病理性肿瘤相关巨噬细胞表型的形成，这或许构成了肿瘤免疫力学与机械免疫学的恶性循环环路。靶向肿瘤内实体应力或巨噬细胞对实体应力的响应，或可打破这一反馈循环，助力肿瘤免疫微环境恢复正常，并改善胶质母细胞瘤对免疫治疗的响应效果。整体实验设计：对经24小时静态实体压迫（负重处理）的RAW264.7巨噬细胞进行RNA测序（RNA-seq）谱分析，并与未受压的琼脂糖对照组进行比对。