Figure 5. SCFAs impair APC activity in vitro and abrogate vancomycin-enhanced RT antitumor activity in vivo.
(A) Bone marrow–derived DCs (bmDCs) were either untreated, treated with 100 μM butyrate (C4), or treated with 100 μM propionate (C3) together with OVA protein (100 μg/mL) for 24 hours before they were plated to an ELISPOT plate with T cells from OT1 mice. (B) Purified T cells were in vitro–stimulated with aCD3/aCD28 in the presence or absence of 100 μM C4/butyrate in a IFN-γ ELISPOT plate. (C) In vivo effects on tumor growth in irradiated mice treated with vancomycin-containing drinking water with or without C4. Mean ± SEM are shown. Statistical significance was assessed by 2-way ANOVA. (D) Ifng mRNA expression levels in tumors from irradiated mice treated with vancomycin-containing drinking water with and without C4/butyrate. Mean ± SEM are shown. Statistical significance was assessed by Tukey’s test. (E) Flow cytometry analysis of OVA-presenting DCs and (F) CD3+CD8+Tet-OVA+ cell subsets. Mean ± SEM are shown. Statistical significance was assessed by Tukey’s test. n = 5 to 10 mice per group. Data are representative of at least 2 independent experiments. *P < 0.05, **P < 0.01.