神经酰胺与前列腺素信号之间的串扰介导了对免疫检查点阻断的耐药

Immunotherapy has revolutionized cancer treatment, yet only a fraction of patients develop durable responses to immune checkpoint blockade (ICB). Identifying tumor-intrinsic mechanisms driving alphaPD-1/alphaPD-L1 resistance remains critical to improving patient outcomes. We recently discovered that reduced ceramide synthase 4 (CerS4) activity and the subsequent loss of C18/20 ceramide impairs response to ICB through intracellular PD-L1/Caprin-1 signaling. To investigate this further, we generated an orthotopic, transplantable TNBC (E0771) model of ICB resistance through serial in vivo alphaPD-L1 exposure, yielding the 2RA cell line. 2RA tumors are refractory to both alphaPD-L1 and alphaPD-1 therapy, and transcriptomic signatures derived from this model strongly predict clinical ICB outcomes, supporting its relevance to human disease. Functionally, 2RA tumors display reduced CerS4 expression, diminished C18/20 ceramide, and increased intracellular PD-L1/Caprin-1 interaction. Bulk RNA-seq revealed marked enrichment in prostaglandin E 2 (PGE₂) signaling, a potent immunosuppressive pathway, in 2RA tumors. Mechanistically, we identified that CerS4 inversely regulates prostaglandin-endoperoxide synthase 2 (Ptgs2, COX-2) expression and PGE₂ production through the PD-L1/Caprin-1 complex, whereby ceramide directly interacts with PD-L1 to restrict Caprin-1 binding. Analysis of TCGA and ICB-treated patient datasets substantiated the CerS4/PD-L1/COX-2 axis across multiple solid tumor subtypes. Immune profiling via flow cytometry and snRNA-seq identified dysfunctional progenitor and effector CD8⁺ T cells as central to impaired ICB response in 2RA tumors. Genetic or pharmacological disruption of the CerS4/PD-L1/PGE₂ axis, achieved through CerS4 restoration or TGF-beta inhibition (LY2157299), restored ICB sensitivity, prolonged survival, and induced tumor rejection in vivo . Targeting PGE 2 production with celecoxib, but not aspirin, further enhanced responses when combined with LY2157299 and alphaPD-1 therapy. Targeted lipidomics and multiplex immunofluorescence (mIF) confirmed that this triple combination potently blocks the ceramide/PGE₂ axis and stimulated CD8 + T cell responses to control tumor growth. Finally, mIF analysis of nivolumab-treated pre-surgical human HNSCC specimens (responders vs. non-responders) corroborated these findings by demonstrating reduced tumor ceramide abundance, elevated PanCK + COX-2 + ceramide lo populations, and decreased intratumoral CD8 + T cell density amongst non-responders. Collectively, these studies (1) establish a relevant model of ICB resistance, (2) define a mechanistic framework linking ceramide metabolism to prostaglandin-mediated immune suppression, and (3) highlight therapeutic strategies to target ICB resistance and improve patient outcomes.