PURPOSE Despite its enormous successes, the overall response rate of cancer immunotherapy remains suboptimal, especially in breast cancer. There is an increased interest in combining immune checkpoint inhibitor with targeted agents to enhance antitumor effect. Anti-angiogenic drugs have been shown to synergize with immune checkpoint blockades, but the optimal setting for combining these two modalities and the underlying mechanisms of synergistic responses are not fully understood. EXPERIMENTAL DESIGN We tested the combination of anti-PD-1 and different doses of VEGFR2-targeting agents in syngeneic breast cancer mouse models. Tumor-infiltrated immune cell subsets were profiled by flow cytometry. A cytokine array was carried out to identify inflammatory changes in different treatment conditions. The efficacy of combined anti-angiogenic and anti-PD-1 therapy was further evaluated in patients with advanced triple-negative breast cancer (TNBC). RESULTS Blockade of VEGFR2 sensitizes breast tumors to PD-1 blockade in a dose-dependent manner. Although both conventional and low-dose anti-VEGFR2 antibody treatments normalize tumor vessels, low-dose VEGFR2 blockade results in more robust immune cell infiltration and activation and promotes the secretion of osteopontin (OPN) by CD8+ T cells. OPN subsequently induces tumor cell production of TGF-β, which in turn upregulates PD-1 expression on immune cells. In patients with advanced TNBC, combined treatment with low-dose anti-VEGFR2 inhibitor and anti-PD-1 demonstrated excellent tolerability and efficacy. Higher OPN and TGF-β expressions correlated with improved treatment responses. CONCLUSIONS Together, these results demonstrate a dose-dependent synergism between anti-angiogenic therapy and immune checkpoint blockade, thus providing important insights into the optimal strategies for combining immunotherapy with molecular-targeted agents.

中文翻译：

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低剂量抗血管生成疗法可使乳腺癌对PD-1阻断敏感。

目的尽管取得了巨大的成功，但癌症免疫治疗的总体应答率仍然不理想，尤其是在乳腺癌中。将免疫检查点抑制剂与靶向药物组合以增强抗肿瘤作用的兴趣日益浓厚。已显示抗血管生成药物可与免疫检查点阻滞协同作用，但结合这两种方式的最佳设置以及协同反应的潜在机制尚不完全清楚。实验设计我们在同系乳腺癌小鼠模型中测试了抗PD-1和不同剂量的VEGFR2靶向药物的组合。通过流式细胞仪分析肿瘤浸润的免疫细胞亚群。进行细胞因子阵列鉴定不同治疗条件下的炎症变化。在晚期三阴性乳腺癌（TNBC）患者中进一步评估了抗血管生成和抗PD-1联合治疗的疗效。结果VEGFR2的阻断使乳腺肿瘤对PD-1的阻断呈剂量依赖性。尽管常规和低剂量抗VEGFR2抗体治疗均能使肿瘤血管正常化，但低剂量VEGFR2阻断可导致更强力的免疫细胞浸润和激活，并促进CD8 + T细胞分泌骨桥蛋白（OPN）。OPN随后诱导肿瘤细胞产生TGF-β，进而上调免疫细胞上PD-1的表达。在晚期TNBC患者中，低剂量抗VEGFR2抑制剂和抗PD-1的联合治疗显示出优异的耐受性和疗效。较高的OPN和TGF-β表达与改善的治疗反应相关。