iPSC-Derived Neoantigen-Specific CTL Therapy for Ewing Sarcoma

• Published in: Cancer immunology research 2021-10, Vol.9 (10), p.1175-1186
• Main Authors: Ishii, Midori, Ando, Jun, Yamazaki, Satoshi, Toyota, Tokuko, Ohara, Kazuo, Furukawa, Yoshiki, Suehara, Yoshiyuki, Nakanishi, Mahito, Nakashima, Kazutaka, Ohshima, Koichi, Nakauchi, Hiromitsu, Ando, Miki
• Format: Article
• Language: English
• Subjects: Animals; Cell Line, Tumor; Cell Proliferation; Cell- and Tissue-Based Therapy; Female; Gene Expression Regulation, Neoplastic; Humans; Induced Pluripotent Stem Cells - metabolism; Mice; Oncogene Proteins, Fusion - genetics; Proto-Oncogene Protein c-fli-1 - genetics; RNA-Binding Protein EWS - genetics; Sarcoma, Ewing - genetics; Sarcoma, Ewing - pathology; Sarcoma, Ewing - therapy; Xenograft Model Antitumor Assays
• ISSN: 2326-6066; 2326-6074
• DOI: 10.1158/2326-6066.cir-21-0193

The prognosis of Ewing sarcoma caused by fusion is poor, especially after metastasis. Although therapy with CTLs targeted against altered EWS/FLI1 sequences at the gene break/fusion site may be effective, CTLs generated from peripheral blood are often exhausted because of continuous exposure to tumor antigens. We addressed this by generating induced pluripotent stem cell (iPSC)-derived functionally rejuvenated CTLs (rejT) directed against the neoantigen encoded by the fusion gene. In this study, we examined the antitumor effects of EWS/FLI1-rejTs against Ewing sarcoma. The altered amino acid sequence at the break/fusion point of EWS/FLI1, when presented as a neoantigen, evokes an immune response that targets sarcoma. Although the frequency of generated EWS/FLI1-specific CTLs was only 0.003%, we successfully established CTL clones from a healthy donor. We established iPSCs from a EWS/FLI1-specific CTL clone and redifferentiated them into EWS/FLI1-specific rejTs. To evaluate cytotoxicity, we cocultured EWS/FLI1-rejTs with Ewing sarcoma cell lines. EWS/FLI1-rejTs rapidly and continuously suppressed the proliferation of Ewing sarcoma for >40 hours. Using a Ewing sarcoma xenograft mouse model, we verified the antitumor effect of EWS/FLI1-rejTs via imaging, and EWS/FLI1-rejTs conferred a statistically significant survival advantage. "Off-the-shelf" therapy is less destructive and disruptive than chemotherapy, and radiation is always desirable, particularly in adolescents, whom Ewing sarcoma most often affects. Thus, EWS/FLI1-rejTs targeting a Ewing sarcoma neoantigen could be a promising new therapeutic tool.