Gastric cancer-derived exosomal indoleamine 2,3 dioxygenase 1 drives immunosuppression in gastric cancer by suppressing dendritic cell maturation

Figure 3 Gastric cancer-derived exosomes suppress the maturation and immunostimulatory function of dendritic cells by delivering indoleamine 2,3 dioxygenase 1. Bone marrow-derived dendritic cells were stimulated with lipopolysaccharide to induce maturation and incubated with 100 μg/mL unmodified exosomes, indoleamine 2,3 dioxygenase 1 (IDO1)-silenced exosomes, and negative control exosomes, respectively. A: MKN45 cells were transfected with short hairpin RNA targeting IDO1 or short hairpin RNA targeting negative control, and IDO1 protein levels were measured using Western blot analysis; B: IDO1 protein levels in isolated exosomes were measured using Western blot analysis; C: IDO1 protein levels in dendritic cells were assessed using Western blot analysis; D-G: Representative flow cytometry histograms showing the expression of maturation markers (cluster of differentiation 80, cluster of differentiation 86, and major histocompatibility complex class II) and quantification of the mean fluorescence intensity; H: The secretion levels of interleukin (IL)-12p70 and IL-10 were measured using enzyme-linked immunosorbent assay kits; I: IL-12p70/IL-10 ratio was calculated. Data were presented as mean ± SD. ^aP < 0.01. CD: Cluster of differentiation; exo: Exosomal; GAPDH: Glyceraldehyde-3-phosphate dehydrogenase; IDO1: Indoleamine 2,3 dioxygenase 1; IL: Interleukin; LPS: Lipopolysaccharide; MFI: Mean fluorescence intensity; MHC: Major histocompatibility complex; PBS: Phosphate buffered saline; sh-IDO1: Short hairpin RNA targeting indoleamine 2,3 dioxygenase 1; sh-NC: Short hairpin RNA targeting negative control.