Sustained IFN signaling, however, can contribute to the expression of the immune checkpoint programmed death-ligand (PD-L)1 and to PD-L1-independent adaptive resistance leading to tumor relapse in an in vivo study combining RT and immune checkpoint inhibitors (ICI), anti-CTLA4 and anti-PD-L1 [80]. Here, IFNA1 is linked to neoplasm.