TGFB1 and neoplasm: This RT-induced overexpression of PD-L1 by tumor cells can take place either via the production of IFN-γ by RT-activated T cells in immunogenic tumors, as well as in poorly immunogenic tumors where there is concomitant TGF-β blockade [11,63], or via RT-mediated upregulation of HIF-1α, as discussed above [64,65,66].