Fig 2: Exosomes derived from gastric cancer tissues promoted metastasis of the tumor through the SCF/c-KIT signaling pathway in vivo. (A) The electron micrograph image of the exosomes from gastric cancer tissue and control gastric tissue (MFC-Exo, Control-Exo) (Bar = 200 nm). (B) The sizes of MFC-Exo and Control-Exo were analyzed using NTA. (C) Western blot analysis of MFC-Exo, Control-Exo. CD81, CD9, TSG101, and CD63 were exosomal markers. Calnexin was the negative marker. Cells were used as a control. (D) Western blot analysis of SCF and CD9 in Control-Exo and MFC-Exo. (E) A gastric cancer metastasis model was established by injecting MFC cells into the tail vein of C57 mice, and exosomes or antibodies were administered via the tail vein after 10 days. The metastasis of MFC was monitored using an IVIS at 10 days, 15 days, 20 days, 25 days, 30 days, and 35 days. (F) Hematoxylin and eosin (H&E) staining of lung metastatic tumor 35 days after MFC cell injection (Bar = 100 μm). The ns indicated no significance, *p < 0.05, ***p < 0.001, ****p < 0.0001, ###p < 0.001, ####p < 0.0001. Abbreviations: exosome (Exo).

Fig 3: Exosomes derived from gastric cancer tissues activated mast cell degranulation through the SCF/c-KIT signaling pathway, thereby promoting angiogenesis in vivo. (A) Immunohistochemistry (IHC) staining of c-KIT in lung metastatic tumor 35 days after MFC cell injection (Bar = 100 μm). (B) IHC staining of Tryptase in lung metastatic tumor 35 days after MFC cell injection (Bar = 100 μm). (C) Concentration of histamine, TNF-α, MCP-1, Tryptase, and CXCL1 in mouse serum assessed by ELISA. (D) immunofluorescence (IF) staining of CD31 and p-ERK in lung metastatic tumor 35 days after MFC cell injection (Bar = 100 μm). The ns indicated no significance, ***p < 0.001, ****p < 0.0001, ▼▼▼▼p < 0.0001.

Fig 4: Gastric cancer cell exosomes promoted mast cell recruitment and degranulation by activating the SCF/c-KIT signal pathway. (A) qRT-PCR analysis of SCF expression in AGS and MKN1 cells transfected with sh-SCF or sh-NC. (B) Western blot analysis of SCF expression in AGS and MKN1 cells after transfection with sh-SCF or sh-NC. (C) Western blot analysis of SCF expression in exosomes derived from AGS and MKN1 cells after transfection with sh-SCF or sh-NC (sh-SCF-Exo, sh-NC-Exo). (D) Detection of β-hexosaminidase release in LAD2 mast cells after different treatments. (AGS and MKN1: PBS, sh-NC-Exo (40 μg/mL), sh-SCF-Exo (40 μg/mL), sh-NC-Exo (40 μg/mL) + IgG, sh-NC-Exo (40 μg/mL) + Briquilimab (10 nM)). (E) Concentration of histamine, TNF-α, MCP-1, Tryptase, and IL-8 in mast cell supernatant was assessed by ELISA after different treatments. (F) The recruitment of LAD2 mast cells after co-culture with AGS or MKN1 in different groups (sh-NC, sh-SCF, sh-NC + IgG, sh-NC + Briquilimab (10 nM)) (Bar = 100 μm). **p < 0.01, ***p < 0.001, ****p < 0.0001, ###p < 0.001, ####p < 0.0001, ▼▼▼▼p < 0.0001. Abbreviations: exosome (Exo).