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 tumour cells that activate NKG2D
on cytotoxic immune cells and mediate NKG2D-dependent, antigen-independent
tumour 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 between USP14, PARP1 and NFIL3, while an intracranial tumour
model combined USP14 inhibition and immunotherapy to evaluate effects on
tumourigenesis and antitumour 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 antitumour immunity. Clinical glioma specimens showed
USP14 overexpression was correlated with PARP1 and dysfunctional CD8⁺
T-cell infiltration. Collectively, 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.