Estradiol promotes cell survival and induces Greb1 expression in granulosa cell tumors of the ovary through an ER alpha-dependent mechanism

Granulosa cell tumor (GCT) is a form of ovarian tumor characterized by its tendency to recur years after surgical ablation. Little is known about the mechanisms involved in GCT development and progression. GCTs can produce estradiol (E2), but whether this hormone could play a role in this cancer through its nuclear receptors, i.e. ER alpha and ER beta, remains unknown. Here, we addressed this issue by cell-based and molecular studies on human GCTs and GCT cell lines. Importantly, we observed that E2 significantly increased the growth of GCT cells by promoting cell survival. The use of selective agonists of each type of receptor, together with Esr1 (ER alpha) or Esr2 (ER beta)-deleted GCT cells, revealed that E2 mediated its effects through ER alpha-dependent genomic mechanisms and ER beta/ER alpha-dependent extra-nuclear mechanisms. Notably, the expression of Greb1, a prototypical ER target gene, was dose-dependently upregulated by E2 specifically through ER alpha in GCT cells. Accordingly, using GCTs from patients, we found that GREB1 mRNA abundance was positively correlated to intra-tumoral E2 concentrations. Tissue microarray analyses showed that there were various combinations of ER expression in primary and recurrent GCTs, and that ER alpha expression persisted only in combination with ER beta in similar to 40% of recurrent tumors. Altogether, this study demonstrates that E2 can promote the progression of GCTs, with a clear dependence on ER alpha. In addition to demonstrating that GCTs can be classified as a hormone-related cancer, our results also highlight that the nature of ER forms present in recurrent GCTs could underlie the variable efficiency of endocrine therapies. (C) 2022 The Pathological Society of Great Britain and Ireland.