摘要 : Plain language summary The anti-PD-1 antibody shows potential as an anticancer therapy for tumors, including gastric cancer. However, the antitumor effect of the anti-PD-1 antibody alone is unsatisfactory. The tumor microenvironme... 展开 Plain language summary The anti-PD-1 antibody shows potential as an anticancer therapy for tumors, including gastric cancer. However, the antitumor effect of the anti-PD-1 antibody alone is unsatisfactory. The tumor microenvironment (TME) is an environment in which a tumor develops and survives. The TME comprises heterogeneous molecules and cell types, including immune cells, endothelial cells and fibroblasts, besides cancer cells. This study aimed to explore the effects of low-dose chemotherapy on the TME and its antitumor effect when combined with anti-PD-1 antibody. The TME was analyzed using the flow cytometry method. Although low-dose paclitaxel and low-dose 5-fluorouracil changed the TME, both failed to enhance the antitumor activity when combined with the anti-PD-1 antibody. Aim: This study aimed to explore the effects of low-dose chemotherapy in the tumor microenvironment (TME) on a gastric cancer xenograft and its antitumor activity combined with the anti-PD-1 antibody. Materials & methods: Mice with gastric cancer were divided into four groups. The body weight and tumor volume of the mice were recorded. The TME was analyzed using flow cytometry. Results: Low-dose paclitaxel increased the PD-L1 expression level and the number of CD8(+) T cells, but not the CD4(+) T and myeloid-derived suppressor cells or PD-1(+) CD8(+) T cells in the TME. Low-dose 5-fluorouracil reduced the number of myeloid-derived suppressor cells and PD-1(+) CD8(+) T cells, but the PD-L1 expression level and the number of CD4(+) T and CD8(+) T cells did not change in the TME. The anti-PD-1 antibody inhibited tumor growth, but the combination therapy did not show superior antitumor activity. Conclusion: Low-dose chemotherapy altered the TME but failed to improve the responses to the anti-PD-1 antibody. 收起