Epigenetic Regulation of Uterine Smooth Muscle Tumors: Histone Modifications in Uterine Fibroids and Leiomyosarcoma.

Uterine smooth muscle tumors (USMTs) represent a diverse group of neoplasms arising from the myometrium, ranging from benign uterine fibroids (leiomyomas) to highly aggressive uterine leiomyosarcoma. While genetic alterations contribute to tumor development, growing evidence highlights the crucial role of epigenetic regulation in shaping tumor behavior. Among these mechanisms, histone modification has emerged as a key regulator of chromatin structure and gene expression. Histone modifications, including acetylation, methylation, phosphorylation, ubiquitination, ADP-ribosylation, and SUMOylation, are dynamically controlled by epigenetic regulators known as writers, erasers, and readers, which collectively modulate transcriptional programs involved in cell proliferation, differentiation, and stress responses. Recent studies indicate that dysregulation of histone-modifying enzymes contributes to the pathogenesis of USMTs by altering chromatin accessibility and transcriptional networks. In uterine fibroids, histone modifications are associated with hormone-responsive signaling pathways, extracellular matrix deposition, and abnormal smooth muscle cell proliferation. In contrast, uterine leiomyosarcoma exhibits extensive epigenetic reprogramming characterized by aberrant histone acetylation and methylation patterns, dysregulated chromatin regulators, and activation of oncogenic signaling pathways that promote tumor aggressiveness and genomic instability. Importantly, histone modifications interact with other epigenetic mechanisms, including DNA methylation, non-coding RNA-mediated regulation, and RNA epitranscriptomics, forming complex networks that influence tumor initiation and progression. This narrative review summarizes current knowledge on histone modification pathways and their roles in USMT biology, highlighting the functions of histone-modifying enzymes, their interactions with other epigenetic mechanisms, and their impact on tumor development. In addition, this review discusses emerging therapeutic strategies targeting epigenetic regulators, including inhibitors of histone deacetylases, histone methyltransferases, and readers, as well as potential epigenetic biomarkers for diagnosis and prognosis. Finally, this review outlines future research directions, including multi-omics integration, and advanced epigenomic technologies, which may provide deeper insights into the epigenetic landscape of USMTs and facilitate the development of personalized therapeutic approaches.