Abstract 2886: Investigation of tumor-intrinsic activated Wnt/B-catenin signaling in immune avoidance of HCC

Abstract Background: Recent evidence have indicated several tumor-intrinsic oncogene pathways in T cell exclusion and immune evasion of cancers . In hepatocellular carcinoma (HCC), Wnt/β-catenin (CTNNB1) signaling activation is highly prevalent and has been reported to be associated with an immune avoided tumor microenvironment. ICG-001 is a small molecule inhibitor that prevents β-catenin from binding to cyclic AMP response element-binding protein (CBP) by competitively binding itself to CBP. The inhibition of CBP/β-catenin selectively induces apoptosis in transformed cells and have shown tumor suppressive effects in several cancers. Aim: This study aims to investigate the role of tumor-intrinsic Wnt/β-catenin pathway in controlling the expression of chemoattractants in HCC that influence immune cell migration into the tumor site. Methods: We established a syngeneic C57BL/6 mouse model using a hepatoma murine Hepa1-6 isogenic cell line to allow us to interrogate how gain-of-function CTNNB1 mutation (S45P) affects immune surveillance and response to ICG-001 in HCC. The mice were divided into two groups and were subcutaneously injected with either Hepa1-6 vector (n=29) or Hepa1-6 CTNNB1 (S45P) (n=29). At day 6, each group were subdivided into two treatment groups: ICG-001 and untreated. The effect of ICG-001 on immune infiltrates was investigated by Opal multiplex fluorescent immunohistochemistry (IHC) in formalin-fixed, paraffin-embedded (FFPE) tissues. Results: Untreated mice bearing CTNNB1 (S45P) HCCs (n=15) showed larger tumor growth in comparison to their vector controls (n=14), suggesting CTNNB1 (S45P) conferred a more aggressive clone. After a week of ICG-001 treatment by continuous osmotic pump perfusion, 42.9% (6/14) of CTNNB1 (S45P) mice showed a positive response to ICG-001, where a tumor regressed volume was indicated in 4 mice and stable disease in 2 mice. Progressive disease with continuous tumor growth, on the other hand, was shown in all untreated mice. Multiplex fluorescent IHC of tumors obtained from ICG-001 treated CTNNB1 (S45P) mice showed an increased influx of M1 macrophage and CD8 T cells in the tumor site compared to an immune avoidance phenotype in untreated controls. Accordingly, our vector control group did exhibit response to ICG-001 when compared to their respective untreated groups. Based on these findings, it is plausible that CTNNB1 activation impairs the expression of chemoattractant in HCC, and prevents immune cell migration into the tumor site. Consequently, we further examined tumor tissues for chemokine expressions and found higher levels of CXCL9, CXCL10 and CXCL11 in ICG-001 treated CTNNB1 (S45P) when compared to their untreated control groups. In conclusion, our results suggested Wnt/β-catenin activation plays a role in immune evasion and contribution to a “cold” immune tumor microenvironment in HCC. Citation Format: Aikha Melissa Go Wong, Alissa Michelle Go Wong, Loucia KY Can, Joseph Kwong, Anthony WH Chan, Jinna Chen, Michael Kahn, Nathalie Wong. Investigation of tumor-intrinsic activated Wnt/B-catenin signaling in immune avoidance of HCC [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 2886.