β-Catenin Induces Transcriptional Expression of PD-L1 to Promote Glioblastoma Immune Evasion

PD-L1 up-regulation in cancer contributes to immune evasion by tumor cells. Here, we show that Wnt ligand and activated EGFR induce the binding of the β-catenin/TCF/LEF complex to the CD274 gene promoter region to induce PD-L1 expression, in which AKT activation plays an important role. β-Catenin depletion, AKT inhibition, or PTEN expression reduces PD-L1 expression in tumor cells, enhances activation and tumor infiltration of CD8+ T cells, and reduces tumor growth, accompanied by prolonged mouse survival. Combined treatment with a clinically available AKT inhibitor and an anti-PD-1 antibody overcomes tumor immune evasion and greatly inhibits tumor growth. In addition, AKT-mediated β-catenin S552 phosphorylation and nuclear β-catenin are positively correlated with PD-L1 expression and inversely correlated with the tumor infiltration of CD8+ T cells in human glioblastoma specimens, highlighting the clinical significance of β-catenin activation in tumor immune evasion.