RAPA-resistant mTOR negatively regulates B7-H1 expression by reducing STAT3 activation independent of FoxO. (A) WT or IRF-1–null BM cell cultures were exposed to Torin1 (100 nM), stimulated with LPS (100 ng/mL) overnight on day 7, and CD11c+ DCs interrogated for B7-H1 expression by flow cytometry on day 8. (B) Quantification of B7-H1 MFI from panel A relative to DMSO control. *P < .05 compared with WT. (C) DMSO or Torin1-exposed DCs were cultured as described in “Methods.” STAT3 inhibitor VII (250 nM) was added to cultures 2 hours before LPS stimulation for 18 hours, and B7-H1 expression analyzed on CD11c-gated DCs. (D) Quantification of B7-H1 MFI from panel C across multiple experiments normalized to DMSO control DC expression. *P < .05 compared with the corresponding group not receiving STAT3 inhibitor VII. (E) FoxO1/3/4fl/fl × ROSA26-CreERT2 BM cells were exposed to 4OHT, and B7-H1 expression determined on CD11c-gated DCs on day 8. (F) Quantification of B7-H1 MFI from panel E normalized to the DMSO+EtOH group. Data are from n = 2 to 4 independent experiments.
