Macrophages reprogramming improves immunotherapy of IL-33 in peritoneal metastasis of gastric cancer
Peritoneal metastasis (PM) has a suppressive tumor immune microenvironment (TIME), which limits the effects of immunotherapy. This study aims to investigate the immunomodulatory effects of intraperitoneal administration of IL-33 on PM-associated TIME. Immunocompetent mice were used to investigate the role of IL-33 in development of abdominal dissemination and host outcome. Murine (m) and human (h) gastric cancer cells were tested for their response to IL-33 by qRT-PCR, flow cytometry, and immunofluorescence. Survival was significantly prolonged in patients with high Il-33 mRNA expression. Intraperitoneal administration of IL-33 could induce the celiac inflammatory environment, activate immunologic effector cells and reverse the immunosuppressive tumor microenvironment, which delayed tumor progression and peritoneal metastasis of gastric cancer. Mechanistically, IL-33 could induce M2 polarization by activating p38-GATA-binding protein 3 (GATA3) signaling pathway. IL-33 combined with anti-CSF1R or p38 inhibitor to regulate tumor-associated macrophages (TAMs) showed synergistic anti-tumor effect. Intraperitoneal administration of IL-33 inducing local inflammatory milieu provided a novel approach for the treatment of metastatic peritoneal malignancies, which combined with TAMs reprogramming to reshape TIME could achieve better treatment efficacy. Overall design: To investigate the immunomodulatory effects of intraperitoneal administration of IL-33 on peritoneal metastasis-associated tumor immune microenvironment, we established abdominal dissemination tumor model by challenging 615-line mice with mouse forestomach carcinoma cells.