Splicing-mediated control of hnRNPD isoform switching by SRSF2 drives PD-L1-dependent immune evasion in gallbladder cancer.

Gallbladder cancer (GBC), a lethal malignancy of the biliary tract, is associated with a poor clinical prognosis. Although chemo-immunotherapy combinations demonstrate preliminary efficacy, the molecular determinants of treatment response remain elusive. Emerging evidence implicates aberrant alternative splicing in modulating tumor immunity. Through an in vitro CRISPR/Cas9 screen, we identified SRSF2 as a key RNA-binding protein regulating PD-L1 expression. Intriguingly, SRSF2 does not directly bind PD-L1 mRNA. Multi-omics analyses (mRNA-seq, RIP-seq, and proteomics) revealed that SRSF2 induces exon skipping in hnRNPD, shifting isoform expression from full-length P45 to truncated P40. Functional studies established that P45-but not P40-binds to AU-rich elements in the PD-L1 3'-UTR to promote mRNA degradation. Leveraging this mechanism, we designed splice-switching antisense oligonucleotides (ASOs) that block SRSF2-mediated exon skipping, restoring P45 expression. This intervention effectively reduced PD-L1 levels and potentiated T-cell-mediated cytotoxicity in vitro and in vivo. These findings elucidate a splicing-centric mechanism of immune evasion and highlight the therapeutic potential of splicing modulation in cancer immunotherapy. Proposed model of the SRSF2-hnRNPD-PD-L1 axis in gallbladder cancer (GBC) immune evasion and its therapeutic targeting. Overexpression of SRSF2 drives hnRNPD exon skipping, shifting the isoform balance from the PD-L1-degrading P45 to the truncated P40. This transition stabilizes PD-L1 mRNA and facilitates tumor immune evasion. Conversely, therapeutic intervention with splice-switching ASOs blocks SRSF2-mediated alternative splicing, restores P45 expression, and effectively reactivates T-cell-mediated cytotoxicity against GBC cells.