Abstract 5180: T cell receptor repertoire analysis revealed tissue tropism of tumor-reactive T-cell clones in cell cycle reporter mice
Authors: Tsunoda Mikiya , Aoki Hiroyasu , Takahashi Munetomo , Shimizu Haruka , Ogiwara Haru , Shichino Shigeyuki , Matsushima Kouji , Ueha Satoshi 
Published: April 2023

Abstract
Tumor-reactive T cells are composed of clones with various TCRs, and each clone has different in vivo kinetics. By analyzing TCR repertoire of tumor and tumor-draining lymph node (dLN), we have demonstrated that Tumor-reactive CD8+ T cells can be classified into “dLN Major”, “Tumor Major”, and “Double Major” clones, which exhibited high frequency in the dLN, tumor, or both tissues. To investigate whether this classification was related to the tissue tropism in the proliferation of each clone, we here employed tumor-bearing Fucci transgenic mice expressing a fluorescent cell-cycle indicator to identify the proliferation of T-cell clones in each tissue. We purified proliferating- and resting-CD8+ T cells from the tumors and dLN and analyzed their TCR repertoire in an LLC subcutaneous tumor model. All Tumor Major clones were proliferated in the tumor, while nearly 0% for dLN Major, indicated their different proliferative capacity in the tumor. The percentage of proliferating clones in the dLN was 20% for Tumor Major and 15% for dLN Major, indicating that these clones had equivalent proliferative capacity in the dLN. These proliferating dLN major clones overlapped more with the tumor than the non-proliferating dLN major clones, suggesting that proliferating dLN Major clones had higher tumor migration capacity. Furthermore, these proliferating dLN major clones were more proliferative in the tumor. These results suggested that dLN Major responded to antigen presentation in the dLN but not in the tumor, whereas Tumor Major responded to those in the dLN and tumor. In addition, there are two types of dLN major, “clones that are proliferating in dLN” and “clones that are not proliferating in dLN” indicating that the former may contribute to the anti-tumor response. Immune checkpoint inhibitor (ICI) treatment not only reactivates clones in the tumor but also activates tumor-reactive clones in the dLN. In conformity with these previous studies, the percentage of proliferating clones among dLN Major increased to about 50% and 80% in the dLN in mice with anti-PD-L1 and anti-CD4 treatment, respectively. This result suggests ICI treatment enhances anti-tumor responses mainly by promoting the activation and proliferation of dLN Major clones. This study shows new findings that tumor-reactive T cells differ in the tissue tropism of their proliferation of each clone. In the future, a quantitative understanding of the contribution of each class of clones to the anti-tumor response will hopefully lead to the development of new combined immunotherapies that optimize the anti-tumor T-cell response.
Citation Format: Mikiya Tsunoda, Hiroyasu Aoki, Munetomo Takahashi, Haruka Shimizu, Haru Ogiwara, Shigeyuki Shichino, Kouji Matsushima, Satoshi Ueha. T cell receptor repertoire analysis revealed tissue tropism of tumor-reactive T-cell clones in cell cycle reporter mice. [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 5180.