Abstract 872: Noninvasive monitoring of endogenous Pdl1 expression by using a dual reporter system

Abstract

Abstract Programmed death-ligand 1 (Pdl1) is a key immune checkpoint protein facilitating tumor escape from host immune system. Clinical approval of anti-PD1 and anti-PDL1 antibodies for the treatment of a variety of malignancies underscores the promise of immune checkpoint therapy. Further progress in this promising area of research is likely to come from better understanding of the mechanisms for regulation of immune checkpoint proteins such as PDL1. In the present study, we designed a dual reporter imaging system to monitor Pdl1 expression by use of the CRSPR-Cas9 technology. A fusion reporter that consists of eGFP and Luc2 was introduced into downstream of the endogenous Pdl1 gene, right before the stop codon, through CRISPR-Cas9 mediated homologous recombination. A P2A self-cleaving motif is inserted between the fusion reporter gene (eGFP-Luc2) and Pdl1. The reporter system was introduced into two murine tumor cell lines, 4T1 and B16F10. In vitro, an increase in eGFP intensity and bioluminescence of the reporter cells was observed after exposure to ionizing radiation or IFN-gamma, which has been reported to upregulate the expression of Pdl1. In vivo, we were able to observe radiation induced increase in bioluminescence signals from tumor established by use of the reporter cells. Our study therefore provided proof of principle for the use of our endogenous Pdl1 reporter imaging system to monitor the expression levels of Pdl1 in vitro and in vivo noninvasively and serially. Citation Format: Min Zhou, Xinjian Liu, Fang Li, Chuan-Yuan Li. Noninvasive monitoring of endogenous Pdl1 expression by using a dual reporter system [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 872. doi:10.1158/1538-7445.AM2017-872