DataSheet_1_Fusobacterium nucleatum Facilitates M2 Macrophage Polarization and Colorectal Carcinoma Progression by Activating TLR4/NF-κB/S100A9 Cascade.docx

Fusobacterium nucleatum (Fn) has been considered as a significant contributor in promoting colorectal carcinoma (CRC) development by suppressing host anti-tumor immunity. Recent studies demonstrated that the aggregation of M2 macrophage (Mφ) was involved in CRC progress driven by Fn infection. However, the underlying molecular mechanisms are poorly characterized. Here, we investigated the role of Fn in Mφ polarization as well as its effect on CRC malignancy. Fn infection facilitated differentiation of Mφ into the M2-like Mφ phenotype by in vitro study. Histological observation from Fn-positive CRC tissues confirmed the abundance of tumor-infiltrating M2-like Mφ. Fn-induced M2-like Mφ polarization was weakened once inhibiting a highly expressed damage-associated molecular pattern (DAMP) molecule S100A9 mainly derived from Fn-challenged Mφ and CRC cells. In addition, Fn-challenged M2-like Mφ conferred CRC cells a more malignant phenotype, showing stronger proliferation and migration characteristics in vitro and significantly enhanced tumor growth in vivo, all of which were partially inhibited when S100A9 was lost. Mechanistic studies further demonstrated that activation of TLR4/NF-κB signaling pathway mediated Fn-induced S100A9 expression and subsequent M2-like Mφ activation. Collectively, these findings indicate that elevated S100A9 in Fn-infected CRC microenvironment participates in M2-like Mφ polarization, thereby facilitating CRC malignancy. Furthermore, targeting TLR4/NF-κB/S100A9 cascade may serve as promising immunotherapeutic strategy for Fn-associated CRC.

具核梭杆菌（Fusobacterium nucleatum, Fn）被认为是通过抑制宿主抗肿瘤免疫，从而促进结直肠癌（colorectal carcinoma, CRC）发生发展的关键致病菌。近期研究表明，M2型巨噬细胞（M2 macrophage, Mφ）的聚集参与了Fn感染驱动的CRC进展，但其具体分子机制尚未得到充分阐释。本研究旨在探究Fn对巨噬细胞极化的调控作用，及其对CRC恶性表型的影响。体外实验证实，Fn感染可促进巨噬细胞极化为M2样表型；对Fn阳性CRC组织的组织学观察也验证了肿瘤浸润性M2样巨噬细胞的丰度显著升高。当靶向抑制主要由Fn刺激的巨噬细胞和CRC细胞高表达的损伤相关分子模式（damage-associated molecular pattern, DAMP）分子S100A9后，Fn诱导的M2样巨噬细胞极化过程被显著削弱。此外，经Fn刺激的M2样巨噬细胞可使CRC细胞获得更强的恶性表型：体外实验中表现出更强的增殖与迁移能力，体内实验中肿瘤生长速度显著加快；而当S100A9缺失后，上述效应均得到部分抑制。机制研究进一步证实，TLR4/NF-κB信号通路的激活介导了Fn诱导的S100A9表达及后续的M2样巨噬细胞活化。综上，本研究结果表明，Fn感染的CRC微环境中升高的S100A9参与调控M2样巨噬细胞极化，进而促进CRC的恶性进展。此外，靶向TLR4/NF-κB/S100A9信号轴有望成为Fn相关性CRC的潜在免疫治疗策略。