RPS3 (ribosomal protein S3) was one of the highly expressed proteins in the exosome of SGC7901R cells in comparison with SGC7901S cells, which sparked our interest to explore the role and mechanism of exosomal RPS3 protein in transmitting a chemoresistance phenotype from cisplatin-resistant to cisplatin-sensitive gastric cancer cells. The gene discussed is RPS3; the disease is gastric cancer.