IL-4 together with IL-1β induces antitumor Th9 cell differentiation in the absence of TGF-β signaling

IL-9-producing CD4 ⁺ (Th9) cells are a subset of CD4 ⁺ T-helper cells that are endowed with powerful antitumor capacity. Both IL-4 and TGF-β have been reported to be indispensable for Th9 cell-priming and differentiation. Here we show, by contrast, that Th9 cell development can occur in the absence of TGF-β signaling. When TGF-β was replaced by IL-1β, the combination of IL-1β and IL-4 efficiently promoted IL-9-producing T cells (Th9 ^IL-4+IL-1β ). Th9 ^{IL-4+ IL-1β} cells are phenotypically distinct T cells compared to classic Th9 cells (Th9 ^IL-4+TGF-β ) and other Th cells, and are enriched for IL-1 and NF-κB gene signatures. Inhibition of NF-κB but not TGF-β-signaling negates IL-9 production by Th9 ^IL-4+IL-1β cells. Furthermore, when compared with classic Th9 ^IL-4+TGF-β cells, Th9 ^IL-4+IL-1β cells are less exhausted, exhibit cytotoxic T effector gene signature and tumor killing function, and exert a superior antitumor response in a mouse melanoma model. Our study thus describes an alternative pathway for Th9 cell differentiation and provides a potential avenue for antitumor therapies.