Disrupting USP14-mediated PARP1 dynamics reinstates MIC-A/B-driven antigen-independent CD8(+) T cell killing in glioma.

Antigen loss is a major mechanism of resistance to immunotherapy. MIC-A/B are stress-inducible ligands expressed by tumor cells that activate NKG2D on cytotoxic immune cells and mediate NKG2D-dependent tumor cell killing, yet the mechanisms underlying their reduced expression in glioma remain unclear. Using single-cell RNA sequencing and spatial transcriptomics, we investigated ectopic MIC-A/B in mouse glioma and identified USP14 as a key regulator through deubiquitinase screening. Proteomic, coimmunoprecipitation, chromatin immunoprecipitation, immunofluorescence, and ubiquitination assays characterized the interactions among USP14, PARP1, and nuclear factor, interleukin 3 regulated (NFIL3), while an intracranial tumor model combined USP14 inhibition and immunotherapy to evaluate effects on tumorigenesis and antitumor immunity. We found that MIC-A/B increased CD8(+) T cell infiltration and reversed exhaustion and that USP14 stabilized PARP1 via K63-linked deubiquitination at lysine-653, reducing NFIL3 binding to the MIC-A/B promoter through poly(ADP-ribosyl)ation. Inhibition of USP14 activated CD8(+) T cells in a MIC-A/B-NKG2D-dependent, antigen-independent manner and synergized with PD1 blockade to prolong survival and enhance antitumor immunity. Clinical glioma specimens showed that the USP14 overexpression was correlated with PARP1 and dysfunctional CD8(+) T cell infiltration. These results demonstrate that USP14 inhibition restores MIC-A/B-mediated CD8(+) T cell activation, reverses immune exhaustion, and represents a promising strategy to enhance glioma immunotherapy.