Damage associated molecular patterns (DAMPs), including calreticulin (CRT) exposure, high-mobility group box 1 protein (HMGB1) elevation, and ATP release, characterize immunogenic cell death (ICD) and may play a role in cancer immunotherapy. Triple negative breast cancer (TNBC) is an immunogenic subtype of breast cancer with higher lymphocyte infiltration. Here, we found that regorafenib, a multi-target angiokinase inhibitor previously known to suppress STAT3 signaling, induced DAMPs and cell death in TNBC cells. Regorafenib induced the expression of HMGB1 and CRT, and the release of ATP. Regorafenib-induced HMGB1 and CRT were attenuated following STAT3 overexpression. In a 4T1 syngeneic murine model, regorafenib treatment increased HMGB1 and CRT expression in xenografts, and effectively suppressed 4T1 tumor growth. Immunohistochemical staining revealed increased CD4⁺ and CD8⁺ tumor-infiltrating T cells in 4T1 xenografts following regorafenib treatment. Regorafenib treatment or programmed death-1 (PD-1) blockade using anti-PD-1 monoclonal antibody reduced lung metastasis of 4T1 cells in immunocompetent mice. While regorafenib increases the proportion of MHC II high expression on dendritic cells in mice with smaller tumors, the combination of regorafenib and PD-1 blockade did not show a synergistic effect on anti-tumor activity. These results suggest that regorafenib induces ICD and suppresses tumor progression in TNBC. It should be carefully evaluated when developing a combination therapy with an anti-PD-1 antibody and a STAT3 inhibitor.

损伤相关分子模式 (DAMP)，包括钙网蛋白 (CRT) 暴露、高迁移率族蛋白 1 (HMGB1) 升高和 ATP 释放，是免疫原性细胞死亡 (ICD) 的特征，可能在癌症免疫治疗中发挥作用。三阴性乳腺癌（TNBC）是一种具有较高淋巴细胞浸润的免疫原性乳腺癌亚型。在这里，我们发现瑞戈非尼（一种先前已知可抑制 STAT3 信号传导的多靶点血管激酶抑制剂）可诱导 TNBC 细胞中的 DAMP 和细胞死亡。瑞戈非尼诱导 HMGB1 和 CRT 的表达以及 ATP 的释放。 STAT3 过表达后瑞戈非尼诱导的 HMGB1 和 CRT 减弱。在 4T1 同基因小鼠模型中，瑞格非尼治疗增加了异种移植物中 HMGB1 和 CRT 的表达，并有效抑制 4T1 肿瘤生长。免疫组织化学染色显示，瑞格非尼治疗后 4T1 异种移植物中 CD4 ⁺和 CD8 ⁺肿瘤浸润 T 细胞增加。瑞戈非尼治疗或使用抗 PD-1 单克隆抗体阻断程序性死亡 1 (PD-1) 可减少免疫活性小鼠中 4T1 细胞的肺转移。虽然瑞戈非尼增加了肿瘤较小的小鼠树突状细胞上MHC II高表达的比例，但瑞戈非尼和PD-1阻断剂的组合并没有显示出抗肿瘤活性的协同作用。这些结果表明瑞戈非尼在 TNBC 中诱导 ICD 并抑制肿瘤进展。在开发抗 PD-1 抗体和 STAT3 抑制剂的联合疗法时应仔细评估。