EXTH-18. DEVELOPMENT OF A TRANSGENIC MOUSE MODEL ENABLING COMPARATIVE ANALYSIS OF CHIMERIC ANTIGEN RECEPTOR (CAR)-EXPRESSING IMMUNE CELL POPULATIONS FOR CANCER IMMUNOTHERAPY

Abstract

Abstract We reported the creation of C57BL/6J-background transgenic (Tg) mice carrying the anti-epidermal growth factor receptor (EGFR)vIII-CAR with CD3z-CD28-4-1BB downstream of a Lox-Stop-Lox cassette in the Rosa26 locus. Breeding these mice with CD4-Cre Tg allows rigorous and reproducible evaluation of CAR-T cell therapy in syngeneic models (Chuntova et al. Neuro-Onc 2022). As the extension of the approach, we crossed the EGFRvIII-CAR Tg mice with mice carrying Vav-Cre, which allowed the expression of anti-EGFRvIII CAR in all hematopoietic cells. In particular, we evaluated CAR-T, CAR-NKT, CAR-NK cells, and CAR-macrophages. CAR-NK cells displayed a robust antigen-specific cytolytic activity against EGFRvIII-expressing SB28 cells, comparable to CAR-T cells in vitro and mice bearing intracerebral EGFRvIII-expressing SB28 gliomas. Remarkably, CAR-NKT cells produced higher levels of inflammatory cytokines when co-cultured with EGFRvIII-expressing SB28 cells, such as IFN-g, Perforin, IL4, and IL17. On the other hand, despite their in vitro cytotoxic effects against SB28 cells, CAR-NK cells failed to mediate a therapeutic response in mice bearing intracerebral glioma. Future studies will be directed at improving the in vivo persistence of CAR-NK cells using engineered cytokines, such as IL-2 superkine. In addition, we extensively investigated CAR-macrophages in vitro and in vivo. Unfortunately, we did not observe significant CAR-specific anti-tumor effects. Consequently, we modified the intracellular domain of CAR from CD3z-CD28-4-1BB to CD3z alone. This alteration led to increased TNF-α production through CAR signaling. This transgenic mouse model offers rigorous and reproducible evaluations of CAR-expressing hematopoietic cells. Furthermore, the model provides a platform for developing combination therapies, such as CAR-T plus CAR-NKT or CAR-T plus CAR-NK cells, with potential implications for enhanced cancer treatment strategies.