Loss of VGLL4 suppresses tumor PD-L1 expression and immune evasion.

Abstract Targeting immune checkpoints, such as PD‐L1 and its receptor PD‐1, has opened a new avenue for treating cancers. Understanding the regulatory mechanism of PD‐L1 and PD‐1 will improve the clinical response rate and efficacy of PD‐1/PD‐L1 blockade in cancer patients and the development of combinatorial strategies. VGLL4 inhibits YAP‐induced cell proliferation and tumorigenesis through competition with YAP for binding to TEADs. However, whether VGLL4 has a role in anti‐tumor immunity is largely unknown. Here, we found that disruption of Vgll4 results in potent T cell‐mediated tumor regression in murine syngeneic models. VGLL4 deficiency reduces PD‐L1 expression in tumor cells. VGLL4 interacts with IRF2BP2 and promotes its protein stability through inhibiting proteasome‐mediated protein degradation. Loss of IRF2BP2 results in persistent binding of IRF2, a transcriptional repressor, to PD‐L1 promoter. In addition, YAP inhibits IFNγ‐inducible PD‐L1 expression partially through suppressing the expression of VGLL4 and IRF1 by YAP target gene miR‐130a. Our study identifies VGLL4 as an important regulator of PD‐L1 expression and highlights a central role of VGLL4 and YAP in the regulation of tumor immunity.