Alternative splicing of immune checkpoints: Classifications, mechanisms, and therapeutic implications for overcoming immune checkpoint blockade resistance.

Immune checkpoint blockade (ICB) therapy has revolutionized oncology, yet its clinical efficacy remains limited due to primary and acquired resistance. Alternative splicing (AS), a fundamental post-transcriptional regulatory mechanism in eukaryotic gene expression, has been shown to profoundly remodel immune checkpoint molecules, driving immune evasion and ICB resistance. In this review, we systematically categorize immune checkpoint splicing based on splicing events, evolutionary conservation, altered domains, and functional impacts. We propose a new feature of immune checkpoint splicing, transmembrane exon splicing strategy. Mechanistically, we explain how dysregulated spliceosomes, cis-acting elements, and trans-acting factors within the tumor microenvironment orchestrate these splicing events, impacting ligand/receptor interactions and downstream immune signaling. Therapeutically, soluble isoforms serve as diagnostic/prognostic biomarkers. Engineered oncolytic viruses expressing soluble decoys offer novel combination strategies. Emerging therapeutic approaches, including antisense oligonucleotides, splicing modulators, RNA interference, and CRISPR/Cas systems, show promise for directly targeting aberrant splicing to overcome ICB resistance.