Targeting the TRIM14/USP14 Axis Enhances Immunotherapy Efficacy by Inducing Autophagic Degradation of PD-L1.

Immunotherapy has greatly improved cancer treatment in recent years by harnessing the immune system to target cancer cells. The first immunotherapeutic agent approved by the US Food and Drug Administration (FDA) was interferon a (IFNa). Treatment with IFNa can lead to effective immune activation and attenuate tumor immune evasion, but persistent treatment has been shown to elicit immune suppressive effects. Here, we identified an autophagy-dependent mechanism by which IFNa triggers tumor immune evasion by upregulating PD-L1 to suppress the anti-tumor activity of CD8+ T cells. Mechanistically, IFNa increased transcription of TRIM14, which recruited the deubiquitinase USP14 to inhibit the autophagic degradation of PD-L1. USP14 removed K63-linked ubiquitin chains from PD-L1, impairing its recognition by the cargo receptor p62 (also known as SQSTM1) for subsequent autophagic degradation. Combining the USP14 inhibitor IU1 with IFNa and anti-CTLA4 treatment effectively suppressed tumor growth without significant toxicity. This work suggests a strategy for targeting selective autophagy to abolish PD-L1-mediated cancer immune evasion.