Hyperthermia improves doxorubicin-based chemotherapy by activating mitochondrial apoptosis in bladder cancer

Purpose: Although intravesical chemotherapy has several antitumoral benefits, it can also have severe side effects. The development of novel therapeutic approaches for bladder cancer (BC) is thus warranted. Hyperthermia (HT) is a widely applicable adjuvant therapy in various cancers. Therefore, this study investigated the effect of HT on improving the chemosensitivity of BC. Materials and Methods: The BC cell lines 5637 and T24 were cultured and treated with HT (43°C) for 24 h. Then, cell viability and survival were assessed using resazurin reagent and colony formation assay, respectively. Western blot assay was used to analyze the levels of Bax, Bcl-2, cleaved caspase-3, and cleaved poly (ADP-ribose) polymerase (PARP) protein expression. Mitochondria degradation was observed by MitoTracker Green staining. Results: In BC cells, HT co-administered with various concentrations of doxorubicin significantly inhibited cell viability and survival. Moreover, HT combined with doxorubicin promoted mitochondrial apoptosis, which caused Bax upregulation and Bcl-2 downregulation. Levels of cleaved caspase-3 and PARP protein expression were also elevated after co-treatment. Conclusion: Taken together, HT improved the chemosensitivity of BC cells to doxorubicin. HT combined with chemotherapy further activated mitochondrial apoptosis in BC cells. The findings suggested that HT may serve as a potential adjunctive treatment for BC that is ready to be applied clinically.