The efficacy of plasma exosomal miRNAs as predictive biomarkers for PD-1 blockade plus chemotherapy in gastric cancer.

[BACKGROUND] The response of gastric cancer (GC) patients to first-line programmed cell death 1 (PD-1) blockade and S-1 plus oxaliplatin (SOX) chemotherapy varies considerably, and the underlying mechanisms driving this variability remain elusive. Exosomal microRNAs (miRNAs or miRs) have emerged as potential biomarkers for efficacy prediction due to their roles in GC biology and stable expression in serum. In this study, we aimed to identify biomarkers to predict patients' response to anti-PD-1 therapy and further elucidate the potential mechanisms by which these exosomal miRNAs modulate the immune response in GC.

[METHODS] Serum exosomes were extracted from 11 GC patients (five in the primary cohort and six in the validation cohort) treated with SOX and camrelizumab (a PD-1 inhibitor). High-throughput sequencing was performed to identify miRNA expression profiles, after which hierarchical clustering and a differential expression analysis were conducted. Functional enrichment analyses of the target genes for the significantly upregulated miRNAs were performed using the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases. The validation of the candidate miRNAs was carried out by quantitative polymerase chain reaction (qPCR) in an independent cohort.

[RESULTS] MiRNA sequencing identified 3,083 miRNAs, of which 74 (42 upregulated and 32 downregulated) were differentially expressed between the responders and non-responders. The GO and KEGG pathway analyses of the top 20 upregulated miRNAs indicated that the target genes were significantly involved in transcription regulation, cytoplasmic processes, and protein binding, and that key pathways included the PI3K-AKT, MAPK, RAP1, and RAS signaling pathways. Consistent with the sequencing findings, the qPCR validation results showed significant differences in the expression levels of miRNA451a and miRNA142-5p between the responders and non-responders.

[CONCLUSIONS] This study identified specific plasma exosomal miRNAs in GC patients that differ between responders and non-responders to PD-1 monoclonal antibody therapy combined with chemotherapy. These miRNAs could serve as predictive biomarkers, paving the way for precision medicine and personalized therapy in the treatment of GC.