P220-1: CDK8 in Treg differentiation

Immune health requires innate and adaptive immune cells to engage precisely balanced pro- and anti-inflammatory forces. A holistic understanding of how individual small molecules affect this balance is essential to anticipate immune-related side effects, select mitigating immunomodulatory therapies and highlight novel utility as immunomodulators. We previously showed that the high-specificity, low-toxicity cyclin dependent kinase 8 (CDK8) inhibitor DCA promotes tolerogenic effects in innate immune cells. Here, we demonstrate that DCA exerts a novel profile of tolerogenic activity on CD4+ T cells, promoting Treg and Th2 while inhibiting Th1 and Th17 differentiation. DCA enhances human Treg differentiation and our models demonstrate clear tolerogenic function of DCA-driven Tregs in the absence of confounding contribution from DCA-innate immune interactions. DCA engages unique mechanisms, including specifically enhancing early Foxp3 expression via regulating c-Jun phosphorylation, to promote Treg differentiation. CDK8 inhibitors are currently being developed to treat cancer; our findings suggest that the potential blunting of host-versus-tumor effects may warrant ancillary pro-inflammatory agents. Importantly, these results highlight novel utility of DCA as an immunomodulator, not only in vivo, but also in ex vivo cellular therapy. All cells from 4 sets of 2 B6.FOXP3GFP M mice. CD4+CD62L+GFP- cells were sorted for RNA and culture. Cells were cultured in Treg_lo (TGFb 1.5 ng/ml), Treg_DCA (TGFb 1.5 ng/ml + 100nM DCA) or Treg_hi (TGFb 10 ng/ml) conditions (1 ug/ml ea plate-coated anti-CD3/CD28). Aliquots were taken at d1, d2 and d4 post-stimulation. D1 and D2 samples were sorted for total, GFP+ and GFP- populations; D4 was sorted for GFP+ from Treg_DCA and Treg_hi conditions only. First analyses should compare naive vs D2 GFP+ and GFP- from Treg_lo/DCA. The goal would be to determine qualitative differences in FOXP3+ populations between Treglo, Treghi & TregDCA.