Abstract 7259: Effectiveness and comparison of CAR-T cell therapies for synovial sarcoma; HER2-targeted CAR-T and NKG2D-based CAR-T

Abstract

Abstract Introduction: In Japan since 2019, CAR-T cell therapy has been used to treat patients with relapsed or refractory B-cell acute lymphoblastic leukemia and diffuse large B-cell lymphoma and has shown excellent clinical results. Clinical studies of CAR-T cell therapies targeting various antigens, such as HER2, have been conducted, but the therapeutic outcome in sarcoma is still limited. We have previously reported that HER2-targeted CAR-T cells show antitumor effects for synovial sarcoma in vitro. The purpose of this study is to compare HER2-targeted CAR-T cells and NKG2D-based CAR-T cells in antitumor effect and specific responses for synovial sarcoma in vitro. Materials and Methods: Surface expressions of HER2 and NKG2D ligands on three synovial sarcoma cell lines were detected by using recombinant human HER2 Fc chimeric protein and that of NKG2D, followed by staining with PE-conjugated anti-human IgG secondary antibody. We generated 4-1BB-type second generation CAR-T cells targeting NKG2D ligands and examined their antitumor effects and specific responses against synovial sarcoma cells. In addition, we compared the differences between HER2-targeted CAR-T cells and NKG2D-based CAR-T cells by co-culturing with synovial sarcoma cells using short-term assay (WST-8 assay), long-term assay (Real-time Cell Analysis) and CD107a assay. Results: HER2 and NKG2D ligands were found to be expressed by flow cytometry in three synovial sarcoma cell lines. In vitro, NKG2D-based CAR-T cells showed antitumor effects against synovial sarcoma cells, including degranulation and cytokine production. Furthermore, NKG2D-based CAR-T cells showed stronger antitumor effects than HER2-targeted CAR-T cells in both short- and long-term assays and expressed higher levels of CD107a. Conclusions: In this study, NKG2D-based CAR-T cells showed more antitumor effects than HER2-targeted CAR-T cells in vitro. Although the reason for this is not clear, we hypothesize that NKG2D ligands may be induced in synovial sarcoma cells by co-culture with CAR-T cells because HER2 is a cancer-specific antigen, whereas NKG2D ligands are ligands for activating receptors of natural killer cells. Further studies, including in vivo studies, will be conducted to verify the difference in anti-tumor effects between these CAR-T cells. Citation Format: Tomohiro Miyazaki, Chihaya Imai, Naoki Oike, Yudai Murayama, Takashi Ariizumi, Minori Baba, Yasushi Kasahara, Hiroyuki Kawashima. Effectiveness and comparison of CAR-T cell therapies for synovial sarcoma; HER2-targeted CAR-T and NKG2D-based CAR-T [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7259.