Ma Zemeng, Hao Xiaoyao, Qu Shuang, Zhang Quanli, Luo Jiajing, Li Hongyan, Liu Jinyu, Dai Wenwen, Li Jun, Gu Shouyong, Zhu Dihan, Chen Mingjiu, Zen Ke
State Key Laboratory of Natural Medicines, School of Life Science and Technology, China Pharmaceutical University, Nanjing, 639 Longmian Avenue, Nanjing, Jiangsu 211198, China.
State Key Laboratory of Pharmaceutical Biotechnology, Nanjing University School of Life Sciences, Nanjing, Jiangsu 210093, China.
J Immunother Cancer. 2025 Apr 10;13(4):e010580. doi: 10.1136/jitc-2024-010580.
Sialic acid-binding immunoglobulin-like lectin (Siglec)-15-expressing tumor-associated macrophages (TAMs) drive immunosuppression in the tumor microenvironment (TME), promoting CD8 T cell exhaustion and limiting immunotherapy efficacy. Both blockade of immune checkpoint molecule Siglec-15 and promotion of granulocyte-macrophage colony-stimulating factor (GM-CSF) have been respectively employed in anticancer immunotherapy.
Murine CT26 or MC38 cancer cells were used to establish subcutaneous tumor models in BALB/c or C57BL/6 mice. Tumors were treated with anti-Siglec-15 antibody-GM-CSF chimera (anti-S15×GM CSF) or anti-Siglec-15 antibody via intraperitoneal injection. The TME was analyzed by flow cytometry and ELISA for immune cell infiltration and cytokine levels. Biodistribution and half-life of anti-S15×GM CSF were assessed by intravenous injection in tumor-bearing mice, with GM-CSF levels measured by ELISA. Macrophage reprogramming and antigen presentation were evaluated using bone marrow-derived macrophages and human peripheral blood mononuclear cell-derived macrophages treated with anti-S15×GM CSF, followed by flow cytometry and immunofluorescence assays.
Here we report that anti-S15×GM CSF displays superior function to suppress the progression of Siglec-15-overexpressing MC38 colon cancer engrafted in mice compared to anti-Siglec-15 antibody or GM-CSF alone. Different from the injected GM-CSF which is distributed broadly in various organs and tissues of mouse, the injected anti-S15×GM CSF is preferentially accumulated in Siglec-15-positive tumor cells and TAMs. Anti-S15×GM CSF not only extends the half-life of GM-CSF in vivo, but also reduces the off-target effect of GM-CSF through TAM-specific delivery. In addition to Siglec-15 blockade, anti-S15×GM CSF effectively reprograms immunosuppressive TAMs to a proinflammatory phenotype, enhancing antigen presentation by macrophages to activate T cells.
In summary, our results reveal that anti-S15×GM CSF may serve as an effective therapeutic approach for solid tumors.
表达唾液酸结合免疫球蛋白样凝集素（Siglec）-15的肿瘤相关巨噬细胞（TAM）在肿瘤微环境（TME）中驱动免疫抑制，促进CD8 T细胞耗竭并限制免疫治疗效果。免疫检查点分子Siglec-15的阻断和粒细胞-巨噬细胞集落刺激因子（GM-CSF）的促进分别已被应用于抗癌免疫治疗。
使用小鼠CT26或MC38癌细胞在BALB/c或C57BL/6小鼠中建立皮下肿瘤模型。通过腹腔注射用抗Siglec-15抗体-GM-CSF嵌合体（抗S15×GM CSF）或抗Siglec-15抗体治疗肿瘤。通过流式细胞术和ELISA分析TME中的免疫细胞浸润和细胞因子水平。通过在荷瘤小鼠中静脉注射评估抗S15×GM CSF的生物分布和半衰期，用ELISA测量GM-CSF水平。使用骨髓来源的巨噬细胞和用抗S15×GM CSF处理的人外周血单核细胞来源的巨噬细胞，然后通过流式细胞术和免疫荧光测定评估巨噬细胞重编程和抗原呈递。
我们在此报告，与单独的抗Siglec-15抗体或GM-CSF相比，抗S15×GM CSF在抑制接种于小鼠的Siglec-15过表达MC38结肠癌进展方面表现出优异的功能。与广泛分布于小鼠各种器官和组织中的注射GM-CSF不同，注射的抗S15×GM CSF优先积聚在Siglec-15阳性肿瘤细胞和TAM中。抗S15×GM CSF不仅延长了GM-CSF在体内的半衰期，还通过TAM特异性递送降低了GM-CSF的脱靶效应。除了Siglec-15阻断外，抗S15×GM CSF有效地将免疫抑制性TAM重编程为促炎表型，增强巨噬细胞的抗原呈递以激活T细胞。
总之，我们的结果表明抗S15×GM CSF可能是实体瘤的一种有效治疗方法。
