Discovery of Thermal Sensitizers That Inhibit Heat-Induced SAFB Granule Formation

Hyperthermia is a minimally invasive cancer treatment based on heat stress-induced apoptosis. Its therapeutic efficacy, however, is often limited by tumor heterogeneity and acquired thermotolerance. Therefore, combination strategies involving hyperthermia and chemotherapy have been developed to enhance the therapeutic efficacy. Previously, we showed that SB366791 enhanced heat-induced apoptosis by inhibiting heat stress-induced scaffold attachment factor B (SAFB) granule formation, although its proapoptotic activity was insufficient. Therefore, we screened to identify novel compounds that enhance heat-induced apoptosis by suppressing SAFB granule formation. We identified four hit compounds that inhibited SAFB granule formation, all exhibiting thermal enhancement ratios > 1.0─that significantly enhanced heat-induced apoptosis efficiency. Additionally, the tumor volume in mice treated with a combination of Z19024498 and hyperthermia was significantly smaller than that in mice treated with hyperthermia or Z19024498. These results indicate that the identified compounds, specifically Z19024498, have potential as thermal sensitizers for hyperthermia therapy.