Signaling intact membrane-bound IL-15 enables potent anti-tumor activity and safety of CAR-NK cells
Xiaodi Xu, Peiyu Cao, Meng Wang, Yan Wan, Shu-Wen Sun, Yuxin Chen, Yilin Liu, Tong Su, Ge Gao, Xinze Liu, Weixiang Zhong, Xi Chen, Xiaoyuan Lu, Buze Chen, Junnian Zheng, Gang Wang, Huizhong Li
Abstract
Background Chimeric antigen receptor (CAR)-NK cells are a promising and safe alternative to CAR-T cells. However, the limited persistence in vivo restricts their clinical application and sustained therapeutic responses. IL-15 has been extensively used to improve CAR-NK cell persistence and effectiveness. Nevertheless, accumulation of IL-15 might induce uncontrolled proliferation of CAR-NK cells and thus lead to fatal side-effects. Therefore, it is essential to develop a safe and effective alternative strategy to improve the persistence and anti-tumor activity of CAR-NK cells. Methods A signaling intact membrane-bound IL-15 (mbIL-15) was designed by fusing IL-15 and full-length IL-15Rα and was systematically compared with secretory IL-15 (sIL-15) in a B7H3-targeting CAR-NK cell system regarding their functionality and safety through various in vitro and in vivo experiments. Results Both expression of sIL-15 or mbIL-15 significantly enhanced the proliferation by activating STAT5 and improved anti-tumor activity of CAR-NK cells in vitro and in vivo . Although CAR-NK cells with sIL-15 quickly eliminated intraperitoneal ovarian cancer, the mice experienced severe consequences, including dysregulated CAR-NK cell expansion, intense inflammatory responses, and irreversible organ damages. In contrast, CAR-NK cells carrying mbIL-15 showed moderate cell proliferation and potent tumor killing activity without observable adverse effects in both local treatment and systemic administration models. Conclusion Head-to-head comparative studies demonstrated that signaling intact mbIL-15 significantly improved therapeutic efficacy and safety of CAR-NK cells compared to sIL-15, which provided preclinical evidence for future clinical development.