IRE1a regulates macrophage polarization, PD-L1 expression and tumor growth

We show that the UPR and the IRE1a -XBP1 axis are activated in macrophages during tumor growth, that the conditional knock-out of IRE1a in macrophages regulates the acquisition of a mixed pro-inflammatory/immune suppressive phenotype and is also sufficient to restrain tumor development in vivo. Importantly, we discovered that IRE1a signaling regulates PD-L1 expression in murine and in tumor-infiltrating macrophages in humans.