Institute of Biotherapy, School of Laboratory Medicine and Biotechnology, Southern Medical University, Guangzhou 510515, China.
Shenzhen Ruipuxun Academy for Stem Cell & Regenerative Medicine, 14 Jinhui Road, Shenzhen 518118, China.
Int J Mol Sci. 2022 Apr 1;23(7):3944. doi: 10.3390/ijms23073944.
The acidic tumor microenvironment stands as a major obstacle to the efficient elimination of tumor cells. Norcantharidin (NCTD) is a powerful antitumor agent with multiple bioactivities. However, the effect of NCTD under acidic conditions is still unclear. Here, we report that NCTD can efficiently kill bladder cancer (BC) cells in acidic culture, and more intriguingly, NCTD can induce immunogenic cell death (ICD), thereby promoting antitumor immunity. In NCTD-treated BC cells, the surface-exposed calreticulin (ecto-CALR) was significantly increased. Consistently, co-culture with these cells promoted dendritic cell (DC) maturation. The NCTD-induced ICD is autophagy dependent, as autophagy inhibition completely blocked the NCTD-induced ecto-CALR and DC maturation. In addition, the DC showed a distinct maturation phenotype (CD80 CD86) in acidic culture, as compared to that in physiological pH (CD high CD86). Finally, the NCTD-induced ICD was validated in a mouse model. NCTD treatment significantly increased the tumor-infiltrating T lymphocytes in MB49 bladder cancer mice. Immunizing mice with NCTD-treated MB49 cells significantly increased tumor-free survival as compared to control. These findings demonstrate that NCTD could induce ICD in an acidic environment and suggest the feasibility to combine NCTD with anticancer immunotherapy to treat BC.
酸性肿瘤微环境是有效消除肿瘤细胞的主要障碍。去甲斑蝥素（NCTD）是一种具有多种生物活性的强大抗肿瘤药物。然而，NCTD 在酸性条件下的作用尚不清楚。在这里，我们报告 NCTD 可以在酸性培养条件下有效地杀死膀胱癌（BC）细胞，更有趣的是，NCTD 可以诱导免疫原性细胞死亡（ICD），从而促进抗肿瘤免疫。在 NCTD 处理的 BC 细胞中，表面暴露的钙网蛋白（ecto-CALR）明显增加。一致地，与这些细胞共培养促进树突状细胞（DC）成熟。NCTD 诱导的 ICD 是自噬依赖性的，因为自噬抑制完全阻断了 NCTD 诱导的 ecto-CALR 和 DC 成熟。此外，与生理 pH（CD high CD86）相比，酸性培养中的 DC 表现出明显的成熟表型（CD80 CD86）。最后，在小鼠模型中验证了 NCTD 诱导的 ICD。NCTD 处理显著增加了 MB49 膀胱癌小鼠肿瘤浸润的 T 淋巴细胞。与对照组相比，用 NCTD 处理的 MB49 细胞免疫接种的小鼠肿瘤无进展生存率显著提高。这些发现表明 NCTD 可以在酸性环境中诱导 ICD，并提示将 NCTD 与抗癌免疫疗法相结合治疗 BC 的可行性。
