LncRNA NEAT1 promotes immunosuppression in gastric cancer under endoplasmic reticulum stress by maintaining the M6A methylation of SEMA3A in CAFs

Despite PD1 inhibitors offering new gastric cancer therapies, disease burden persists. Cancer-associated fibroblasts were found to be important in gastric cancer regarding tumor promotion and immunosuppression, but its role in gastric cancer under endoplasmic reticulum stress remained unknown. We conducted mass spectrometry in cancer-associated fibroblasts and transcriptomic-seq in exosomes from gastric cancer, combined with single-cell RNA sequencing analysis and spatial transcriptome sequencing analysis in gastric cancer to uncover the cellular crosstalk. Endoplasmic reticulum stressed models were established, and the isolation of primary cells and exosomes were used to uncover the communication between gastric cancer cells and cancer-associated fibroblasts. RNA pull-down, RIP-qPCR, flow cytometry detection and ELISA were used to demonstrate the interaction and immunity function in gastric cancer under endoplasmic reticulum stress. Moreover, we developed αvβ3-targeted cationic liposomes delivering siRNA of lncRNA NEAT1 towards tumor cells in gastric cancer in vivo. We found m6A protein METTL3, SEMA3A and lncRNA NEAT1, which interacts with METTL3, were highly expressed in cancer-associated fibroblasts under endoplasmic reticulum stress. Endoplasmic reticulum stress stimulation enhanced exosome secretion from gastric cancer cells and significantly elevated the expression of lncRNA NEAT1 in cancer-associated fibroblasts. LncRNA NEAT1 upregulated METTL3 in CAFs, which resulted in the enhanced m6A methylation of SEMA3A mRNA and amplified Treg-mediating immunosuppression. The combination therapy of siNEAT1@Lip-cRGD and anti-PD1 boosted T-cell infiltration and suppressed tumor growth in vivo. Our study unveiled the lncRNA NEAT1/METTL3/SEMA3A axis stimulated by endoplasmic reticulum stress that sustained gastric cancer immunosuppression, providing a rationale for targeting this pathway to improve immunotherapy efficacy.