CAF-secreted LOX promotes PD-L1 expression via histone Lactylation and regulates tumor EMT through TGFβ/IGF1 signaling in gastric Cancer

In gastric cancer treatment, cancer-associated fibroblasts (CAF) may significantly influence the efficacy of immune checkpoint inhibitors by modulating PD-L1 expression. However, the precise mechanisms remain unclear. This study aims to explore the relationship between CAF and PD-L1 expression, providing new insights for improving PD-L1-targeted therapies. Using primary fibroblasts, transcriptome sequencing, ChIP-qPCR, and a lung metastasis model, we discovered that CAF secrete lysyl oxidase (LOX), which activates the TGFβ signaling pathway in gastric cancer cells, thereby promoting insulin-like growth factor 1(IGF1) expression. Upregulation of IGF1 enhances gastric cancer cell migration, epithelial-mesenchymal transition (EMT), and glycolysis. Additionally, we found that lactate accumulation leads to lysine 18 lactylation on histone H3 (H3K18la), which enriches at the PD-L1 promoter region, thus promoting PD-L1 transcription. These findings suggest that CAF may diminish the effectiveness of PD-1/PD-L1 blockade immunotherapy through LOX-induced glycolysis and lactate accumulation. Consequently, we have constructed a model of the interactions among CAF, lactate, and PD-L1 in gastric cancer progression, providing new experimental evidence for PD-L1-based immunotherapy.