Next, we examined the efficacy of NRF2 siRNA delivery in PDT sensitization of 4 additional types of cancer cells: human breast carcinoma cell line MCF7, colon carcinoma cell line HCT116, renal carcinoma cell line A498, and glioblastoma cell line A172. These cells were incubated for 48 h with the NRF2 shRNA-containing lentiviral particle and then subjected to PDT. Subsequently, cellular ROS level was assessed as a marker of PDT efficacy. The level of knockdown was not as high as in the stable cell line. Nevertheless, lentiviral delivery of shRNA significantly reduced the level of NRF2 mRNA in each cell line: 44% reduction in HCT116, 35% reduction in MCF7, 22% reduction in A498, and 38% reduction in A172 (Fig. 9A–9D). Under conditions of NRF2 depletion, PDT-induced ROS was substantially increased in all cell types. These data confirmed the beneficial effects of NRF2 siRNA for sensitizing cancer cells to PDT