PDE5A+ cancer-associated fibroblasts enhance immune suppression in gastric cancer

Background Gastric cancer (GC) ranks among the most prevalent lethal tumours globally. Cancer-associated fibroblasts (CAFs) are pivotal in creating an immunosuppressive tumour microenvironment (TME) in GC. Objective Identifying a critical subpopulation of CAFs in promoting an immunosuppressive TME and enabling immune evasion, which may influence therapeutic effectiveness of immune checkpoint inhibitors (ICIs) for GC. Design We performed single-cell RNA sequencing on 24 patients with GC and spatial transcriptomic profiling on formalin-fixed paraffin-embedded tissue sections from patients and controls. Integrating these data, we mapped cell types and gene signatures and identified distinct CAF subpopulations in the TME that influenced immunotherapy response in patients with GC. In vitro and in vivo studies further elucidated the molecular mechanisms, enhancing therapeutic implications. Results In patients with GC, phosphodiesterase type 5A (PDE5A) expression was associated with shorter overall survival and the formation of immunosuppressive TME. We identified PDE5A + CAFs that were associated with TME alterations, including T cell exclusion and reduced CD8 + cytotoxic T lymphocyte infiltration, potentially impairing the efficacy of immunotherapy in GC. PDE5A + CAFs were observed to promote the epithelial–mesenchymal transition of GC cells through remodelling extracellular matrix. Furthermore, PDE5A + CAFs, via triggering of the PI3K/AKT/mTOR signalling pathway, released CXCL12, which engaged the CXCR4 receptor, consequently recruiting CD8 + TEX + LAG3 T cells to facilitate the development of immunosuppressive TME. The combined treatment of LAG3 blockade and PDE5A inhibitor vardenafil effectively enhanced immunotherapy responses, significantly curbing GC progression in mouse models. Conclusions Our study elucidates the intricate role of PDE5A + CAFs in shaping the immunosuppressive TME in GC, providing mechanistic insights and therapeutic potential for combating this aggressive malignancy.