Hormone receptor expression profile of low-grade serous ovarian cancers

Low-grade serous ovarian carcinomas (LGSOCs) are a histological subtype of epithelial ovarian tumors, accounting for fewer than 5% of all cases of ovarian carcinoma. Due to the chemoresistant nature of this subtype a search for more effective systemic therapies is actively ongoing, hormonal therapy showing some degree of activity in this clinical setting. The present study ought to investigate the hormone receptor status of LGSOCs, as a strategy to provide molecular support for patient-tailored hormonal treatments.

Estrogen receptor α (ERα), ERβ isoforms (i.e. ERβ1, ERβ2 and ERβ5), progesterone and androgen receptor (PR, AR) expression was evaluated by immunohistochemistry in 25 untreated LGSOC primary tumors, 6 matched metastases and 6 micropapillary variant of serous borderline tumors (micropapillary SBOTs). In vitro cellular models were used to provide insights into clinical observations.

Our results showed prominent expression of nuclear ERα, ERβ2, ERβ5 and PR in LGSOC primary tissues, while metastatic lesions also exhibit considerable cytoplasmic ERβ2 levels. Notably, a higher expression of ERβ1 protein was determined in micropapillary SBOTs compared to LGSOCs. In vitro experiments on LGSOC cell lines (i.e. HOC-7 and VOA-1056) revealed low/absent ERα, PR and AR protein expression, whereas the three ERβ isoforms were all present. Proliferation of HOC-7 and VOA-1056 was not modulated by either the endogenous or the selective synthetic ligands.

These novel findings highlight the need of assessing relative levels of ERα and ERβ isoforms in the total receptor pool in future clinical studies investigating molecular predictors of response to hormonal therapy in LGSOC.