RISING STARS: Role of MED12 mutation in the pathogenesis of uterine fibroids.

Uterine fibroids (UFs) are benign tumors arising from the uterus, characterized by accumulation of abundant extracellular matrix (ECM) and sex steroid-dependent growth. Women with symptomatic UFs have reduced quality of life and decreased labor productivity. Among the driver gene mutations identified in UFs, mutations in MED12, a component of the cyclin-dependent kinase (CDK) Mediator module, are the most common and observed in 50-80% of UFs. They are gain-of-function mutations and are more frequently observed in Black women and commonly observed even in small UFs. MED12 mutation-positive UFs (MED12-UFs) often develop multiple rather than solitary and have distinct gene expression profiles, DNA methylomes, transcriptomes, and proteomes. Gene expressions related to ECM organization and collagen-rich ECM components are upregulated, and impaired Mediator kinase activity and dysregulation of Wnt/β-catenin signaling are identified in MED12-UFs. Clinically, the UF shrinking effect of gonadotropin-releasing hormone agonists and ulipristal acetate is dependent on the MED12 mutation status. Understanding of characteristics of MED12-UFs and functions of MED12 mutations for UF tumorigenesis may elucidate the pathophysiology of UFs, leading to the development of new therapeutic options in women with symptomatic UFs.