Prolonged IKKβ Inhibition Improves Ongoing CTL Antitumor Responses by Incapacitating Regulatory T Cells

Publication date: 17 October 2017
Source:Cell Reports, Volume 21, Issue 3
Author(s): Christoph Heuser, Janine Gotot, Eveline Christina Piotrowski, Marie-Sophie Philipp, Christina Johanna Felicia Courrèges, Martin Sylvester Otte, Linlin Guo, Jonathan Leo Schmid-Burgk, Veit Hornung, Annkristin Heine, Percy Alexander Knolle, Natalio Garbi, Edgar Serfling, César Evaristo, Friedrich Thaiss, Christian Kurts
Regulatory T cells (Tregs) prevent autoimmunity but limit antitumor immunity. The canonical NF-κB signaling pathway both activates immunity and promotes thymic Treg development. Here, we report that mature Tregs continue to require NF-κB signaling through IκB-kinase β (IKKβ) after thymic egress. Mice lacking IKKβ in mature Tregs developed scurfy-like immunopathology due to death of peripheral FoxP3⁺ Tregs. Also, pharmacological IKKβ inhibition reduced Treg numbers in the circulation by ∼50% and downregulated FoxP3 and CD25 expression and STAT5 phosphorylation. In contrast, activated cytotoxic T lymphocytes (CTLs) were resistant to IKKβ inhibition because other pathways, in particular nuclear factor of activated T cells (NFATc1) signaling, sustained their survival and expansion. In a melanoma mouse model, IKKβ inhibition after CTL cross-priming improved the antitumor response and delayed tumor growth. In conclusion, prolonged IKKβ inhibition decimates circulating Tregs and improves CTL responses when commenced after tumor vaccination, indicating that IKKβ represents a druggable checkpoint.

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Teaser

FoxP3⁺ regulatory T cells prevent autoimmunity but often incapacitate antitumor immunity. Heuser et al. show that IKKβ deficiency or inhibition preferentially decimated these cells but not cytotoxic T cells in vivo. IKKβ inhibition after tumor vaccination improved antitumor immunity, identifying IKKβ as a potential druggable checkpoint.


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