Abstract 6640: Stabilized recombinant trefoil factor 2 (TFF2-CTP) enhances anti-tumor activity of PD-1 blockade in mouse models of colorectal cancer
Authors: Kim Woosook , Fu Na , Duddempudi Phaneendra , Dubeykovskaya Zinaida , Almo Steven , Guha Chandan , Lederman Seth , Wang Timothy 
Published: September 2020

Abstract
Despite remarkable responses to immune checkpoint blockade across multiple tumor types, the clinical benefit in colorectal cancer (CRC) is limited to microsatellite unstable tumors. PD-L1 expression is a negative prognostic marker in CRC but correlates with a better response to PD-1 blockade. Here, we investigated the role of PD-L1 in colorectal tumorigenesis and evaluated the utility of targeting myeloid-derived suppressor cells (MDSCs) in combination with PD-1 blockade in mouse models of CRC. We generated knockin mice that conditionally express the murine Pdl1 gene (R26-LSL-Pdl1-EGFP) and crossed them with LysM-Cre mice to overexpress PD-L1 specifically in the myeloid lineage. Mice received azoxymethane (AOM; 10 mg/kg i.p.) followed one week later with 2.5% dextran sodium sulfate (DSS) in the drinking water for 7 days. AOM/DSS-treated control mice formed tumors at 10 weeks and developed adenocarcinoma at 17 weeks post-AOM. LysM-Cre; R26-PD-L1 mice treated with AOM/DSS showed markedly enhanced colorectal tumorigenesis, with a significant increase in tumor number and size and enlarged spleen. In both groups, AOM/DSS treatment led to a significant expansion of myeloid cells, particularly CD11b+Gr-1+ MDSCs, in the colon and spleen, along with decreased NK cells compared with untreated mice. Notably, AOM/DSS-treated LysM-Cre; R26-PD-L1 mice showed decreased intratumoral CD8+ T cell infiltration compared to control tumors. Furthermore, there was a significant decrease in the percentage of Ki-67+ cells in intratumoral CD8+ T cells, indicating attenuated anti-tumor immunity. Trefoil factor 2 (TFF2), a secreted anti-inflammatory peptide, inhibits colon tumor growth by suppressing the expansion of CD11b+Gr-1+ MDSCs. TFF2 fused with two carboxyl-terminal peptide and three Flag motifs (TFF2-CTP-Flag) prolonged the circulation time in blood but retained bioactivity. We induced tumors in R26-PD-L1 mice with AOM/DSS, administered fusion recombinant TFF2-CTP-Flag (300 ug i.p.) and/or anti-PD-1 (RMP1-14; 200 ug i.p.) three times a week starting at 10 weeks and 14 weeks, respectively, and examined tumors at 18 weeks post-AOM. R26-PD-L1 mice treated with anti-PD-1 + TFF2-CTP showed a marked reduction in tumor growth while anti-PD-1 monotherapy failed to suppress growth. The combination of anti-PD-1 and TFF2-CTP significantly increased tumor-infiltrating CD8+ T cells and concomitantly decreased intratumoral regulatory T cells and CD11b+Gr-1+ myeloid cells. These early findings suggest that TFF2 augments the response rate of CRC to PD-1 blockade, possibly through suppressing MDSC expansion, supporting the potential of TFF2-CTP in combination I-O treatment for CRC. We are currently testing the efficacy of combined TFF2-CTP and anti-PD-1 therapy in the AOM/DSS model with PD-L1-overexpressing LysM-Cre; R26-PD-L1 mice.
Citation Format: Woosook Kim, Na Fu, Phaneendra Duddempudi, Zinaida Dubeykovskaya, Steven Almo, Chandan Guha, Seth Lederman, Timothy Wang. Stabilized recombinant trefoil factor 2 (TFF2-CTP) enhances anti-tumor activity of PD-1 blockade in mouse models of colorectal cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6640.