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 beta-catenin/TCF/LEF complex to the CD274 gene promoter region to induce PD-L1 expression, in which AKT activation plays an important role. beta-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 beta-catenin S552 phosphorylation and nuclear beta-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 beta-catenin activation in tumor immune evasion.