Disruption of RBPJ in liver cancer-infiltrating T cells enhances antitumor immunity through remodeling epigenetic landscape.

Though inhibiting the RBPJ transcription complex reduces PD-L1 expression and alleviates T cell dysfunction in hepatocellular carcinoma (HCC), the tumor immunomodulatory function of RBPJ in T cells is unclear. This study used patient-derived xenograft models to illustrate the role of RBPJ disruption in clinical outcomes and sensitivity to immunotherapy. Immunoprecipitation was performed to identify whether HUWE1 is the E3 ubiquitin ligase for RBPJ. CUT&Tag, ChIP-/ATAC-qPCR, flow cytometry, and CyTOF were used to investigate the molecular mechanism of how RBPJ regulated the function of HCC-infiltrating T cells. Mice with conditional knockout or knock-in of Huwe1 or Rbpj in T cells were used to evaluate their role in the tumor growth. Furthermore, virtual screening, molecular dynamics simulation, immunoprecipitation, and DNA pull-down assays revealed the role of acarbose in RBPJ transcription complex. Our study found that RBPJ expression rose in exhausted T cells, aggravating their exhaustion. Mechanistically, HUWE1 facilitated the K341 ubiquitination of RBPJ through K48 linkage. RBPJ contributed to T cell exhaustion by enhancing the transcription of exhaustion-related genes as a transcription factor, recruiting RUVBL1 to elevate H3K4me3 levels on the promoters of exhaustion-related genes or H3K27ac on their enhancers, and induced the transcription of the KMT2C, thereby increasing H3K4me1 levels on the enhancers of exhaustion-related genes. Furthermore, acarbose-induced damage in the RBPJ transcriptional complex indicated that targeting T cell exhaustion may be a promising HCC treatment. Collectively, our research results indicated that inhibiting the RBPJ in T cells changed the tumor microenvironment from "cold" to "hot".