Midkine-activated TRPA1+ cancer-associated fibroblasts promote immunotherapy resistance in gastric cancer through a WNT5A-mediated treg circuit.

Gastric cancer (GC) derives limited benefit from immune checkpoint blockade (ICB), in part due to stromal-mediated immune suppression. To investigate the underlying mechanisms, we performed single-cell RNA sequencing on 14 GC specimens from patients treated with neoadjuvant ICB. We identified a distinct subset of TRPA1+ cancer-associated fibroblasts (CAFs) maintained by tumor-derived midkine (MDK) through LEF1-dependent transcription under ICB pressure. These TRPA1+ CAFs drive immunosuppression by secreting WNT5A, which polarizes SPP1+ macrophages and subsequently promotes the accumulation of CD25 + FOXP3+ regulatory T cells (Tregs) in the tumor microenvironment. Disrupting this stromal-myeloid-lymphoid axis via WNT5A inhibition or SPP1+ macrophage depletion reduced Treg infiltration and enhanced the antitumor efficacy of anti-PD-L1 therapy in vivo. Our study unveils an MDK-TRPA1 + CAF-mediated mechanism of ICB resistance in GC and highlights the WNT5A-SPP1+ macrophage pathway as a promising target to overcome immunotherapy resistance.