Abstract PO032: Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand (TRAIL)-TRAIL-R Mediates Cholangiocarcinoma Tumor Immune Evasion by Enhancing Myeloid-Derived Suppressive Cell Population
Authors: Loeuillard Emilien , Yang Jingchun , Haidong Dong , Gores Gregory , Ilyas Sumera 
Published: September 2022

Abstract
Background and Aims: Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), a member of TNF superfamily, is predominantly expressed on immune cells. Engagement of TRAIL with its cognate receptor, TRAIL-R (TR), leads to cancer cells apoptosis. Although the anti-tumor role of TRAIL-TR has been extensively studied, TRAIL agonists have had very limited anti-cancer activity in human clinical trials. TRAIL signaling can facilitate the myeloid response. However, this potential immunosuppressive function of TRAIL has not been examined extensively in cancer biology. Cholangiocarcinoma (CCA), a highly lethal biliary tract cancer, has a dense immunosuppressive microenvironment. Accordingly, CCA provides a model to examine the potential immune regulatory function of TRAIL in cancer biology. Methods: Using syngeneic, orthotopic murine models of CCA, (PMID: 29464042), murine CCA cells (SB cells) that express both Trail and Trail receptor (Tr) were implanted into livers of WT Tr− / − and LyzcreTrf/f mice, the latter have a specific deletion of TRAIL-R on myeloid cells. Hence, in this model the host immune cells express Trail but not the receptor; therefore, they would be capable of inducing TRAIL-mediated apoptosis in CCA cells but would be resistant to TRAIL-mediated immunosuppression. After 4 weeks of tumor growth, mice were sacrificed, and tumors were characterized using flow cytometry. Results: We observed that Tr− / − mice had a significant reduction in tumor burden compared to WT mice. Myeloid-derived suppressor cells (MDSCs) were significantly decreased in Tr− / − tumors compared to WT tumors. Implantation of SB cells into LyzcreTrf/f mice resulted in a marked reduction in tumor burden and attenuation of MDSC infiltration compared to Lyzcre mice. In vitro functional studies employing MDSCs from mice deficient in Tr (MDSC-Tr −/−) were carried out. Compared to WT MDSCs, coculture of MDSC-Tr− /- with SB cells resulted in a significant reduction in the proliferation and immunosuppressive function of MDSCs. Moreover, following cocultured with SB cells, immunofluorescence analysis demonstrated that MDSC-Tr− / − had a reduction in the nuclear translocation of the NFkB subunit P65 compared to WT MDSCs. These data suggest that TRAIL-TR augments MDSC proliferation via NFkB. In conclusion, we have demonstrated that Tr− / − mice have a significant reduction in CCA tumor burden and MDSC infiltration. These results indicate that TRAIL-TR facilitates tumor immune escape and progression by fostering MDSC immunosuppressive function and infiltration, in an NFkB-dependent manner. Direct targeting of TRAIL on CCA cells is a potential anti-tumor strategy.
Citation Format: Emilien Loeuillard, Jingchun Yang, Dong Haidong, Gregory Gores, Sumera Ilyas. Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand (TRAIL)-TRAIL-R Mediates Cholangiocarcinoma Tumor Immune Evasion by Enhancing Myeloid-Derived Suppressive Cell Population [abstract]. In: Proceedings of the AACR Special Conference: Advances in the Pathogenesis and Molecular Therapies of Liver Cancer; 2022 May 5-8; Boston, MA. Philadelphia (PA): AACR; Clin Cancer Res 2022;28(17_Suppl):Abstract nr PO032.