The combination of radiation with immune checkpoint inhibitors was reported in some cancers to have synergic effects both locally and distally. Our aim was to assess this combined therapy on both radiated and nonradiated bladder tumors and to characterize the immune landscape within the tumor microenvironment. Murine bladder cancer cells (MB49) were injected subcutaneously in both flanks of C57BL/6 mice. Mice were randomly assigned to the following treatments: placebo, anti-PD-L1 (four intraperitoneal injections over 2 weeks), radiation to right flank (10 Gy in two fractions), or radiation+anti-PD-L1. Tumor digestion, flow cytometry, and qPCR were performed. Log-rank analysis was used for statistical significance. Radiation+anti-PD-L1 group demonstrated statistically significant slower tumor growth rate both in the radiated and nonirradiated tumors (P < 0.001). Survival curves demonstrated superior survival in the combination group compared with each treatment alone (P = 0.02). Flow cytometry showed increased infiltration of immunosuppressive cells as well as CTL in the radiation and combination groups (P = 0.04). Ratio of immunosuppressive cells to CTL shifted in favor of cytotoxic activity in the combination arm (P < 0.001). The qPCR analysis revealed downregulation of immunosuppressive genes (CCL22, IL22, and IL13), as well as upregulation of markers of CTL activation (CXCL9, GZMA, and GZMB) within both the radiated and distant tumors within the combination group. Combining radiation with immune checkpoint inhibitor provided better response in the radiated tumors and also the distant tumors along with a shift within the tumor microenvironment favoring cytotoxic activity. These findings demonstrate a possible abscopal effect in urothelial carcinoma with combination therapy.

中文翻译：

---

PD-1/PD-L1 免疫检查点抑制膀胱癌放射治疗：原位和远位效应

据报道，放射与免疫检查点抑制剂的组合在某些癌症中具有局部和远端的协同作用。我们的目标是评估这种对放射和非放射膀胱肿瘤的联合治疗，并表征肿瘤微环境中的免疫景观。在 C57BL/6 小鼠的两侧皮下注射鼠膀胱癌细胞 (MB49)。小鼠被随机分配接受以下治疗：安慰剂、抗 PD-L1（2 周内四次腹腔注射）、右侧放射（10 Gy，分两次）或放射 + 抗 PD-L1。进行了肿瘤消化、流式细胞术和 qPCR。对数秩分析用于统计显着性。放射+抗PD-L1组在放射和未放射肿瘤中均表现出统计学上显着的减慢肿瘤生长速率（P < 0.001）。生存曲线显示，与单独的每种治疗相比，联合治疗组的生存率更高（P = 0.02）。流式细胞术显示放疗组和联合组中免疫抑制细胞和 CTL 的浸润增加（P = 0.04）。免疫抑制细胞与 CTL 的比率在组合臂中发生有利于细胞毒性活性的变化（P < 0.001）。qPCR 分析揭示了免疫抑制基因（CCL22、IL22 和 IL13）的下调，以及联合组内放射和远处肿瘤中 CTL 激活标志物（CXCL9、GZMA 和 GZMB）的上调。将放射与免疫检查点抑制剂相结合，在放射肿瘤和远处肿瘤中提供了更好的反应，同时肿瘤微环境内的转变有利于细胞毒活性。这些发现表明联合治疗对尿路上皮癌可能产生远隔效应。