新型热休克蛋白 90 靶向光动力治疗联合 PD-1/PD-L1 阻断可诱导针对乳腺癌的强大全身抗肿瘤疗效和远隔效应。

BACKGROUND: We previously demonstrated potent antitumor activity against human breast cancer xenografts using photodynamic therapy (PDT) targeting a novel tumor-specific photosensitizer (HS201), which binds heat shock protein 90 (HS201-PDT). However, induction of systemic antitumor immunity by HS201-PDT alone or by the combination strategy with immune checkpoint blockade has yet to be determined. METHODS: Using unilateral and bilateral implantation models of syngeneic breast tumors (E0771, MM3MG-HER2, and JC-HER3) in mice, we assessed whether HS201-PDT could induce local and systemic antitumor immunity. In an attempt to achieve a stronger abscopal effect for distant tumors, the combination strategy with anti-PD-L1 antibody was tested. Tumor-infiltrating leukocytes were analyzed by single cell RNA-sequencing and receptor-ligand interactome analysis to characterize in more detailed the mechanisms of action of the treatment and key signaling pathways involved. RESULTS: HS201-PDT demonstrated greater tumor control and survival in immune competent mice than in immunocompromised mice, suggesting the role of induced antitumor immunity; however, survival was modest and an abscopal effect on distant implanted tumor was weak. A combination of HS201-PDT with anti-PD-L1 antibody demonstrated the greatest antigen-specific immune response, tumor growth suppression, prolonged mouse survival time and abscopal effect. The most significant increase of intratumoral, activated CD8+T cells and decrease of exhausted CD8+T cells occurred following combination treatment compared with HS201-PDT monotherapy. Receptor-ligand interactome analysis showed marked enhancement of several pathways, such as CXCL, GALECTIN, GITRL, PECAM1 and NOTCH, associated with CD8+T cell activation in the combination group. Notably, the expression of the CXCR3 gene signature was the highest in the combination group, possibly explaining the enhanced tumor infiltration by T cells. CONCLUSIONS: The increased antitumor activity and upregulated CXCR3 gene signature induced by the combination of anti-PD-L1 antibody with HS201-PDT warrants the clinical testing of HS201-PDT combined with PD-1/PD-L1 blockade in patients with breast cancer, and the use of the CXCR3 gene signature as a biomarker.

背景：我们之前使用针对新型肿瘤特异性热休克蛋白 90（HS201）的光动力疗法（PDT）靶向治疗人乳腺癌异种移植物，展示了强大的抗肿瘤活性，该药物与 HS201-PDT 结合。然而，HS201-PDT 单独或与免疫检查点阻断联合治疗策略诱导全身抗肿瘤免疫的能力尚未确定。

方法：我们在小鼠中使用同源乳腺癌肿瘤（E0771、MM3MG-HER2 和 JC-HER3）的单侧和双侧植入模型，评估 HS201-PDT 是否可以诱导局部和全身抗肿瘤免疫。为了实现对远处肿瘤更强的远隔效应，尝试了与抗 PD-L1 抗体联合的联合治疗策略。通过单细胞 RNA 测序和受体-配体相互作用网络分析来分析肿瘤浸润性白细胞，以更详细地描述治疗的作用机制和涉及的关键信号通路。

结果：HS201-PDT 在免疫功能正常的小鼠中比在免疫功能低下的小鼠中表现出更大的肿瘤控制和生存能力，这表明诱导的抗肿瘤免疫的作用；然而，生存时间仍较短，远处植入肿瘤的远隔效应较弱。HS201-PDT 与抗 PD-L1 抗体联合治疗显示出最大的抗原特异性免疫反应、肿瘤生长抑制、延长小鼠生存时间和远隔效应。与 HS201-PDT 单药治疗相比，联合治疗后肿瘤内、激活的 CD8+T 细胞显著增加，耗竭的 CD8+T 细胞减少。受体-配体相互作用网络分析显示，与 CD8+T 细胞激活相关的几个途径，如 CXCL、GALECTIN、GITRL、PECAM1 和 NOTCH，明显增强，在联合组中。值得注意的是，CXCR3 基因特征的表达在联合组中最高，这可能解释了 T 细胞浸润增强。

结论：抗 PD-L1 抗体与 HS201-PDT 联合使用可增强抗肿瘤活性和上调 CXCR3 基因特征，这使得在乳腺癌患者中测试 HS201-PDT 联合 PD-1/PD-L1 阻断具有临床意义，并将 CXCR3 基因特征用作生物标志物。