Enhancement of human bladder carcinoma cell chemosensitivity to Mitomycin C through quasi-monochromatic blue light (λ=453 nm)

Human urothelial bladder carcinoma (uBC) is the second most tumor entity of the urogenital tract. As far as possible, therapy for non-muscle invasive uBC takes place as resection of the tumor tissue, followed by intravesical chemotherapy or immunotherapy. Because of the high recurrence rate of uBC, there is a need for improved efficiency in the treatment. In the present in vitro study we have evaluated a new approach to enhance the cytotoxic efficiency of Mitomycin C (MMC), which is commonly used for intravesical treatment of uBC on the relevant urothelial cancer cell line RT112. For that we used quasi-monochromatic blue light (453±10 nm) at non-toxic dose of 110 J/cm 2 as an additive stimulus to enhance the therapeutic efficiency of MMC (10 µg/ml). We found, that blue light exposure of RT112 cells led to a very strong increase in intracellular production of reactive oxygen species (ROS) and to a significant reduction of all function parameters of mitochondrial respiration, including basal activity and ATP production. Although not being toxic when used as a single impact, together with MMC blue light strongly enhanced the therapeutic efficiency of MMC in the form of significantly enhanced cytotoxicity via apoptosis and secondary necrosis. Our results clearly show that blue light, most likely due to its ability to increase intracellular ROS production and reduce mitochondrial respiration, increased the cytotoxic efficiency of MMC and therefore might represent an effective, low-side-effect, and success-enhancing therapy option in the local treatment of bladder cancer.