β-catenin activation promotes immune escape and resistance to anti-PD-1 therapy in hepatocellular carcinoma

PD-1 immune checkpoint inhibitors have produced encouraging results in hepatocellular carcinoma (HCC) patients. However, what determines resistance to anti-PD-1 therapies is unclear. We created a novel genetically-engineered mouse model of HCC that enables interrogating how different genetic alterations affect immune surveillance and response to immunotherapies. Expression of exogenous antigens in MYC;p53-/- HCCs led to T cell-mediated immune surveillance, which was accompanied by decreased tumor formation and increased survival. Some antigen-expressing MYC;p53-/- HCCs escaped the immune system by upregulating β-catenin (CTNNB1) pathway. Accordingly, expression of exogenous antigens in MYC;CTNNB1 HCCs had no effect, demonstrating that β-catenin promoted immune escape, which involved defective recruitment of dendritic cells and consequently, impaired T cell activity. Expression of chemokine Ccl5 in antigen-expressing MYC;CTNNB1 HCCs restored immune surveillance. Finally, β-catenin-driven tumors were resistant to anti-PD-1. In summary, β-catenin activation promotes immune escape and resistance to anti-PD-1 and could represent a novel biomarker for HCC patient exclusion.