Despite remarkable clinical efficacy of immune checkpoint blockade (ICB) in cancer treatment, ICB benefits for triple-negative breast cancer (TNBC) remain limited. Through pooled in vivo CRISPR knockout (KO) screens in syngeneic TNBC mouse models, we found that deletion of the E3 ubiquitin ligase Cop1 in cancer cells decreases secretion of macrophage-associated chemokines, reduces tumor macrophage infiltration, enhances anti-tumor immunity, and strengthens ICB response. Transcriptomics, epigenomics, and proteomics analyses revealed that Cop1 functions through proteasomal degradation of the C/ebpδ protein. The Cop1 substrate Trib2 functions as a scaffold linking Cop1 and C/ebpδ, which leads to polyubiquitination of C/ebpδ. In addition, deletion of the E3 ubiquitin ligase Cop1 in cancer cells stabilizes C/ebpδ to suppress expression of macrophage chemoattractant genes. Our integrated approach implicates Cop1 as a target for improving cancer immunotherapy efficacy in TNBC by regulating chemokine secretion and macrophage infiltration in the tumor microenvironment.

尽管免疫检查点阻断 (ICB) 在癌症治疗中具有显着的临床疗效，但 ICB 对三阴性乳腺癌 (TNBC) 的益处仍然有限。通过在同基因 TNBC 小鼠模型中合并体内CRISPR 敲除 (KO) 筛选，我们发现癌细胞中 E3 泛素连接酶Cop1的缺失会降低巨噬细胞相关趋化因子的分泌，减少肿瘤巨噬细胞浸润，增强抗肿瘤免疫力，并增强ICB 回应。转录组学、表观基因组学和蛋白质组学分析表明，Cop1通过C/ebpδ蛋白的蛋白酶体降解发挥作用。Cop1底物Trib2用作连接Cop1的支架和C/ebpδ，这导致C/ebpδ的多泛素化。此外，癌细胞中E3 泛素连接酶Cop1的缺失可稳定C/ebpδ，从而抑制巨噬细胞趋化基因的表达。我们的综合方法将Cop1作为通过调节肿瘤微环境中的趋化因子分泌和巨噬细胞浸润来提高 TNBC 癌症免疫治疗效果的靶点。