Synergistic effects of pazopanib and hyperthermia against uterine leiomyosarcoma growth mediated by downregulation of histone acetyltransferase 1

Pazopanib-a multitargeted tyrosine kinase inhibitor with prominent antiangiogenic effects-has shown promise in the treatment of soft-tissue sarcomas. Hyperthermia has been also applied as an adjunctive treatment to chemotherapy for these malignancies. Here, we show that pazopanib and hyperthermia act synergistically in inhibiting uterine leiomyosarcoma (LMS) cell growth. Compared with either treatment alone, the combination of pazopanib and hyperthermia exerted the highest antitumor activity in a xenograft model. Mechanistically, we found that combined treatment with pazopanib and hyperthermia inhibited histone acetyltransferase 1 (HAT1) expression in LMS cells. TheClockelement on theHAT1promoter was critical for pazopanib- and hyperthermia-inducedHAT1downregulation. Inhibition ofHAT1-either by pazopanib and hyperthermia or throughHAT1silencing-was mediated by suppression ofClock. Accordingly, Clock protein reconstitution rescued bothHAT1levels andHAT1-mediated histone acetylation. Immunohistochemistry revealed a higher expression of HAT1 in uterine LMS than in leiomyomas (p = 0.007), with high HAT1 expression levels being associated with poor clinical outcomes (p = 0.007). We conclude that pazopanib and hyperthermia exert synergistic effects against LMS growth by inhibitingHAT1. Further preclinical studies onHAT1as a potential drug target in uterine LMS are warranted, especially in combination with hyperthermia. Key messages Pazopanib and hyperthermia inhibit the growth of leiomyosarcoma. Their combined use inhibits expression in leiomyosarcoma cells. The promoter element is required for downregulation. HAT1 expression is higher in leiomyosarcoma than in leiomyomas. An increased HAT1 expression is associated with poor clinical outcomes.