AIRE is expressed in breast cancer TANs and TAMs to regulate the extrinsic apoptotic pathway and inflammation

Autoimmune regulator (AIRE) is a transcriptional regulator expressed in the thymus and necessary for maintaining immunological self-tolerance. Extra-thymic AIRE expression is rare and a role for AIRE in tumor-associated innate immune cells has not yet been established. In this study we show that AIRE is expressed in human pro-tumor neutrophils. In breast cancer, AIRE was primarily located to tumor associated neutrophils (TANs), and to a lesser extent to tumor associated macrophages (TAMs) and tumor cells. Expression of AIRE in TAN/TAMs, but not in cancer cells, was associated with an adverse prognosis. We show that the functional role for AIRE in neutrophils and macrophages is to regulate expression of immune mediators and the extrinsic apoptotic pathway involving the Fas/TNFR death receptors and Cathepsin G. We here propose that the role for AIRE in TAN/TAMs in breast tumors is to regulate cell death and inflammation, thus promoting tumor progression.