NOS2 and glioblastoma: Using human glioblastoma U87-MG and U251-MG cells sensitized with ALA-induced PpIX in mitochondria, Fahey et al. [61] showed that these cells added substantially to their pre-existing iNOS after being irradiated, i.e., protein levels increased up to 4-fold over a 20 h post-irradiation period (Figure 4A,B).