Blockade of TNF-α/TNFR2 signalling suppresses colorectal cancer and enhances the efficacy of anti-PD1 immunotherapy by decreasing CCR8+ T regulatory cells.

Enrichment of regulatory T cells (Tregs) in the tumour microenvironment (TME) has been recognized as one of the major factors in the initiation and development of resistance to immune checkpoint inhibitors. C-C motif chemokine receptor 8 (CCR8), a marker of activated suppressive Tregs, has a significant impact on the functions of Tregs in the TME. However, the regulatory mechanism of CCR8 in Tregs remains unclear. Here, we reveal that a high level of TNF-α in the colorectal cancer (CRC) microenvironment upregulates CCR8 expression in Tregs via the TNFR2/NF-κB signalling pathway and the FOXP3 transcription factor. Furthermore, in both anti-PD1-responsive and anti-PD1-unresponsive tumour models, PD1 blockade induced CCR8+ Treg infiltration. In both models, Tnfr2 depletion or TNFR2 blockade suppressed tumour progression by reducing CCR8+ Treg infiltration and thus augmented the efficacy of anti-PD1 therapy. Finally, we identified that TNFR2+CCR8+ Tregs but not total Tregs are positively correlated with adverse prognosis in CRC and gastric cancer. Our work reveals the regulatory mechanisms of CCR8 in Tregs and identifies TNFR2 as a promising target for immunotherapy.