Abstract 4106: Non-autonomous enhancement of gPDL1 CAR-T annihilates TNBC development

Abstract

Triple-negative breast cancer (TNBC) is the most aggressive and challenging breast cancer subtype, which does not respond to traditional endocrine and anti-HER2-targeted therapies. PD-L1 is highly enriched in TNBC and has been considered a therapeutic target. Despite the excellent anti-cancer activity, the atezolizumab-based chimeric antigen receptor (CAR) T cells showed a robust off-target effect. In addition, the treatment of solid tumors with CAR-T is limited by abnormal glycosylation in malignant tumors. Targeting glycosylated PD-L1 (gPD-L1) provided tissue specificity against TNBC, implying it can prevent antigen escape and off-target effect. In this study, we generated gPD-L1 CAR-T cells using lentiviral vectors expressing the scFv regions of the anti-gPD-L1 antibody. The gPD-L1 CAR-T cells exhibited antigen-specific activation, cytokine production, and cytolytic activity against TNBCs in vitro and in the xenograft tumors model. CyTOF and single-cell RNA sequencing (scRNA-seq) showed distinct IFNγ-positive cell types. Mechanistically, IFNγ crosstalked with EGFR signaling through Src activation and, in turn, triggered B3GNT3-mediated PD-L1 glycosylation. Inhibition of Src resulted in reduced gPD-L1 expression in TNBC. CRISPR/Cas9 knockout of B3GNT3 in TNBC cells impaired gPD-L1 CAR-T response. As a result of nonautonomous gPDL1 amplification in TNBCs, gPD-L1 CAR-T cells continued to annihilate TNBCs. Additionally, since gPD-L1 CAR-T cells provided higher specificity on TNBC, they had lower normal tissue toxicity. Overall, gPD-L1 CAR-T exhibits excellent anti-tumor activity against TNBCs, and it could be a promising immunotherapy tool to treat TNBCs in clinic. Furthermore, targeting glycosylation moiety on the tumor antigen is a novel approach to lessen CAR-T toxicity in patients. Citation Format: Chia-Wei Li, Shih-Han Wang, Yun-Ju Lai, Jyun Wang, Chun-Tse Kuo, Shih-Duo Hsu Hung, Shou-Hou Liu. Non-autonomous enhancement of gPDL1 CAR-T annihilates TNBC development. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4106.