Blockade of V‐domain immunoglobulin suppressor of T‐cell activation reprograms tumour‐associated macrophages and improves efficacy of PD‐1 inhibitor in gastric cancer

Abstract Background and aims In gastric cancer, the response rate of programmed cell death protein‐1 (PD‐1) inhibitor is far from satisfactory, indicating additional nonredundant pathways might hamper antitumour immunity. V‐domain immunoglobulin suppressor of T‐cell activation (VISTA) has been reported in several malignancies as a novel immune‐checkpoint. Nevertheless, the role of VISTA in gastric cancer still remains obscure. Our purpose is to explore the clinical significance and potential mechanism of VISTA in affecting gastric cancer patients’ survival and immunotherapeutic responsiveness. Methods Our study recruited eight independent cohorts with a total of 1403 gastric cancer patients. Immunohistochemistry, multiplex immunofluorescence, flow cytometry or intracellular flow cytometry, quantitative polymerase chain reaction, western blotting, fluorescence‐activated cell sorting, magnetic‐activated cell sorting, smart‐seq2, in vitro cell co‐culture and ex vivo tumour inhibition assays were applied to investigate the clinical significance and potential mechanism of VISTA in gastric cancer. Results VISTA was predominantly expressed on tumour‐associated macrophages (TAMs), and indicated poor clinical outcomes and inferior immunotherapeutic responsiveness. VISTA + TAMs showed a mixed phenotype. Co‐culture of TAMs and CD8 + T cells indicated that VISTA + TAMs attenuated effective function of CD8 + T cells. Blockade of VISTA reprogrammed TAMs to a proinflammatory phenotype, reactivated CD8 + T cells and promoted apoptosis of tumour cells. Moreover, blockade of VISTA could also enhance the efficacy of PD‐1 inhibitor, suggesting that blockade of VISTA might synergise with PD‐1 inhibitor in gastric cancer. Conclusions Our data revealed that VISTA was an immune‐checkpoint associated with immunotherapeutic resistance. Blockade of VISTA reprogrammed TAMs, promoted T‐cell‐mediated antitumour immunity, and enhanced efficacy of PD‐1 inhibitor, which might have implications in the treatment of gastric cancer.