PPAR? drives IL-33-dependent ILC2 pro-tumoral functions

Group 2 innate lymphoid cells (ILC2s) play a critical role in protection against helminths and in diverse inflammatory diseases by responding to soluble factors such as the alarmin IL-33, that is often overexpressed in cancer. Nonetheless, regulatory factors that dictate ILC2 functions remain poorly studied. Here, we show that peroxisome proliferator-activated receptor gamma (PPAR gamma) is selectively expressed in ILC2s in humans and in mice, acting as a central functional regulator. Pharmacologic inhibition or genetic deletion of PPAR gamma in ILC2s significantly impair IL-33-induced Type-2 cytokine production and mitochondrial fitness. Further, PPAR gamma blockade in ILC2s disrupts their pro-tumoral effect induced by IL-33-secreting cancer cells. Lastly, genetic ablation of PPAR gamma in ILC2s significantly suppresses tumor growth in vivo. Our findings highlight a crucial role for PPAR gamma in supporting the IL-33 dependent pro-tumorigenic role of ILC2s and suggest that PPAR gamma can be considered as a druggable pathway in ILC2s to inhibit their effector functions. Hence, PPAR gamma targeting might be exploited in cancer immunotherapy and in other ILC2-driven mediated disorders, such as asthma and allergy. Group 2 innate lymphoid cells (ILC2s) are a component of type 2 immune response recently described to be involved in the regulation of anti-tumor immune responses. Here, the authors show that the expression of the peroxisome proliferator-activated receptor gamma (PPAP gamma) in human and mouse ILC2 sustains type-2 cytokines secretion and support their pro-tumorigenic role in preclinical cancer models.