Bladder cancer (BLCA) resistance to immune checkpoint inhibitors (ICIs) is a significant treatment challenge. ORMDL3 is a negative regulator of ceramide synthesis; however, its specific role in the immune-suppressive tumor microenvironment (TME) of BLCA remains unclear. This study explores ORMDL3's role in the TME and its potential as a target for ICIs combination therapies.

This study integrated multi-omics data, including RNA sequencing, single-cell RNA sequencing, and spatial transcriptomics, to comprehensively analyze the impact of ORMDL3 on the BLCA TME. Additionally, the effect of ORMDL3 on CD8+ T cell function and its underlying mechanisms were assessed using in vitro and in vivo models, as well as clinical specimens. The anti-cancer effects of targeting ORMDL3 combined with anti-PD-1 treatment were further evaluated in a BLCA mouse model.

Multi-omics analysis revealed that ORMDL3 was highly expressed in anti-PD-1 resistant BLCA samples, accompanied by a decrease in ceramide levels. Further investigation showed that ORMDL3 inhibited the expression of CD8+ T cell-related chemokines, particularly CCL5, thereby creating a non-inflammatory TME that significantly reduced the infiltration and cytotoxic activity of CD8+ T cells. Mechanistically, ORMDL3 suppressed the expression and secretion of CCL5 mRNA by activating an IRE1α-dependent splicing pathway. In mouse models, targeting ORMDL3 combined with anti-PD-1 therapy significantly inhibited BLCA growth. Additionally, ORMDL3 demonstrated potential as a molecular stratification and predictive biomarker for personalized treatment in BLCA.

ORMDL3 is a key molecule in the BLCA TME and provides a novel target for ICIs combination therapies.