Regulatory role for tumor suppressor REST on estrogen receptor (ESR1) expression and leiomyoma pathophysiology

Uterine fibroids, benign tumors of the smooth muscle layer of the uterus, plague approximately 80% of the female population by age 50. While there have been efforts to understand the mechanism behind this pathophysiology, it largely remains unclear. Lack of preclinical animal models that recapitulate aberrant steroid hormone pathways in UL has significantly hampered the development of long-term hormonal therapies for uterine fibroids. In addition, cultured myometrial as well as leiomyoma smooth muscle cells rapidly silence both estrogen receptor alpha (ESR1) and progesterone receptor (PGR) expression through unknown mechanisms, further limiting in vitro mechanistic studies of UL. Previous work by our lab has determined that the loss of REST, a master regulator of epigenetic gene silencing, in leiomyoma results in the upregulation of ESR1 targets and, therefore, estrogen signaling. Using ChIP-PCR, we find that REST is directly associated with the ESR1 genomic locus, playing a role in its epigenetic regulation. ChIP-seq analysis of Rest cKO mouse uterus samples reveals a global role for REST in the regulation of progesterone receptor target genes and highlights alterations in PGR binding within the Esr1 locus. Additionally, we find REST inhibition of ESR1 expression is regulated through the upstream WNT planar cell polarity molecule, PRICKLE1 (PK1). Based on the role of REST in silencing ESR1 expression in cultured myometrial cells, our results support the development of a potential cell culture method to maintain ESR1 expression through REST modulation. Finally, we establish a broad role for REST in epigenetic regulation relevant to leiomyoma pathophysiology.