Bortezomib Is Associated With Stress Responses and Growth Suppression in ELT3 Uterine Leiomyoma Cells

Background: Uterine leiomyomas are the most frequently occurring benign tumors of the female reproductive system and are characterized by excessive proliferation, resistance to apoptosis, and abnormal extracellular matrix (ECM) accumulation. However, the current treatments are limited by recurrence, systemic side effects, and fertility loss, creating a need for novel therapeutic approaches. Bortezomib, a reversible proteasome inhibitor targeting the β5 subunit of the 26S proteasome, is approved for hematologic malignancies but has not been systematically evaluated in uterine leiomyomas. Therefore, the aim of this study was to investigate the effects of bortezomib on Eker rat leiomyoma tumor-derived 3 (ELT3) uterine leiomyoma cells and explore the underlying molecular mechanisms.Methods: We investigated the effects of bortezomib on ELT3 leiomyoma cells. Cell viability and colony formation were assessed to determine the anti-proliferative effects. Apoptosis, cell cycle progression, and intracellular reactive oxygen species (ROS) levels were evaluated. Mechanistic studies included the evaluation of ubiquitin accumulation, ERK signaling, caspase-3 activation, poly(ADP-ribose) polymerase (PARP) cleavage, levels of ECM-related proteins, including Collagen I and Acta2, and autophagy markers, including microtubule-associated protein 1 light chain 3 (LC3) conversion and p62 degradation. Antioxidant co-treatment experiments were performed to assess ROS dependency.Results: Bortezomib markedly reduced cell viability and colony formation, increased apoptotic cell death, and altered cell cycle distribution, with an increase in the gap 2/mitotic (G2/M)-phase population. Co-treatment with antioxidants attenuated apoptosis, suggesting that the cytotoxic effect was mediated by ROS, which were also elevated intracellularly. Mechanistically, bortezomib promoted ubiquitin accumulation and was associated with changes in ERK-associated signaling involved in leiomyoma cell proliferation, activation of caspase-3 and PARP cleavage, downregulation of ECM proteins, and modulation of autophagy, as evidenced by LC3 conversion and differential patterns of p62 expression over time.Conclusion: Bortezomib exerts multifaceted antitumor effects on uterine leiomyoma cells by targeting proliferation, apoptosis, oxidative stress, ECM deposition, and autophagy, thereby providing mechanistic insights and supporting its possible use as a treatment for uterine leiomyomas.