Resiniferatoxin induces death of bladder cancer cells associated with mitochondrial dysfunction and reduces tumor growth in a xenograft mouse model.

Bladder cancer (BC) is the fifth most common non-cutaneous malignancy and the most common form of BC in Western countries is transitional cell carcinoma. Resiniferatoxin (RTX) has found therapeutic usefulness for the treatment of bladder dysfunction but no data are available on its use as chemotherapeutic agent. The aim of this work is to evaluate the use of RTX as new anti-cancer drug in BC therapy. The effects of RTX on cell viability and cell death were evaluated on T24 and 5637 BC cell lines by MTT assay, cell cycle analysis, Annexin-V/PI staining and agarose gel electrophoresis of DNA. Mitochondrial depolarization and ROS production were assessed by flow cytometry. ADP/ATP ratio was measured by bioluminescence and caspase 3 cleavage by Western blot. For in vivo experiments, athymic nude mice, xenografted with T24 cells, received subcutaneous administrations of RTX. Tumor volumes were measured and immunohistochemistry was performed on tumor sections. Our data demonstrated that RTX influences cell cycle and induces necrotic cell death of BC cells by altering mitochondrial function, leading to depolarization, increase in ADP/ATP ratio and ROS production. Moreover, RTX is able to reduce tumor growth in a xenograft mouse model. Overall, we demonstrated that RTX induces necrotic cell death of BC cells and reduces tumor growth in a xenograft mouse model of BC, suggesting RTX as a new potential anti-cancer drug in BC chemotherapy.