Gastrin, CCK-BR, and PD-L1 expression were confirmed by qRT-PCR in the gastric cancer cells...PAS monotherapy (P = 0.023) or PAS in combination with PD-1 Ab (P = 0.0003) resulted in significantly slowed tumor growth and with no metastases observed...PAS vaccination improves the effectiveness of PD-1 Ab therapy in part by decreasing tumor fibrosis...This study suggests that addition of PAS to immune checkpoint antibody therapy in gastric cancer may be beneficial.