Abstract 549: Immune profiling uncovers neo-antigens and TCR repertoire responding to WX-mPD-1 and WX-mPD-L1 immune checkpoint inhibitors in syngeneic mouse xenograft models

Introduction: PD-1 and PD-L1antibodies have shown impressive clinical benefits to cancer patients. However, still a significant number of patients fail to respond to those checkpoint inhibitors. To understand the underlying mechanism, we performed genomic and immune profiling of both tumor tissues and cytotoxic T cells isolated from syngeneic mouse xenograft models treated with in-house WuXi anti-mouse PD-1(WX-mPD-1) and anti-mouse PD-L1 (WX-mPD-L1) antibodies. Material and methods: Syngeneic mouse xenograft models from melanoma cell lines, CloudmanS91 and B16-F10, were used to evaluate the anticancer efficacy of WX-mPD-1 and WX-mPD-L1 antibodies. Cancer cells and xenograft tumors before and after treatment were collected for RNASeq profiling, from which mRNA expression and DNA mutations were called and neo-antigens were predicted. FACS analysis and TCR sequencing were also performed to examine the tumor infiltrating lymphocytes (TILs) population and TCR repertoire diversity, respectively. Results: Among forty-eight established syngeneic models, nine had been tested with WX-mPD-1 and WX-mPD-L1 antibodies as single agent or in combination. More importantly, we have investigated the expression, mutation loads, neo-antigens for responsive model from CloudmanS91 and partially responsive model from B16-F10. CloudmanS91 model had 8 fold increases in mutation loads compared with B16-F10 model. Neo-antigens identified in CloudmanS91 cells were further knocked out to dissect their roles in activating immune response to WX-mPD-1 and WX-mPD-L1 antibodies in vivo. Conclusions: WX-mPD-1 and WX-mPD-L1 antibodies as well as syngeneic tumor models are useful tools for pre-clinical combination and MoA studies for cancer immunotherapy. Analysis of Neo-antigen and TCR repertoire helps us better understand immune response to these antibodies in preclinical settings, and suggest novel approaches to enhance the current immunotherapeutic interventions. Citation Format: Hua Dong, Yan Lu, Qiyao Zhang, Lingling Zhang, Xiaoyue Chen, Guizhu Yang, Shuqun Yang, Miao He, Xuzhen Tang, Yuxin Qin, Yong Zheng, Jiexing Cai, Yong Cang, Shaoyu Yan, Jing Li, Qunsheng Ji. Immune profiling uncovers neo-antigens and TCR repertoire responding to WX-mPD-1 and WX-mPD-L1 immune checkpoint inhibitors in syngeneic mouse xenograft models. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 549.