Expression of ERα, its ERαΔ3 Splice Variant and γ-SYNUCLEIN in Ovarian Cancer: A Pilot Study

Abstract

AIMS: Ovarian cancer has the highest mortality of any gynaecological malignancy; this is due to rapid peritoneal spread of tumour cells and neovascularization. Understanding the mechanisms underlying this is critical to developing early diagnostic or treatment strategies. We devised a pilot study to examine the role of γ-SYNUCLEIN (γ-SYN), oestrogen receptor (ER)α, and the splice variant ERαΔ3. METHODOLOGY: With ethical approval, ovarian tissue was collected from patients (n=24) undergoing oopherectomy for non-ovarian pathology or primary surgery for suspected ovarian cancer. Quantitative gene expression analysis was employed for γ-SYN, ERα, and ERαΔ3. To identify the in situ localization, immunofluorescence for γ-syn was carried out. RESULTS: Ovarian tumour tissue exhibited an elevated expression of γ-SYN and high-grade tumours had an elevated ERαΔ3:ERα ratio compared with benign tissue. The majority of previous studies point to the γ-syn protein being present in epithelial cells of high-grade disease. Our study supports this, but additionally we conclusively identify its presence in the endothelial cells of vasculature surrounding low-grade disease; immunofluorescence was strongest in the apical cells surrounding the lumen. CONCLUSION: Our results demonstrate for the first time that there are readily-expressed levels of γ-SYN and ERαΔ3 in normal ovarian tissue and ovarian tumours. In high-grade disease, γ-syn and an elevated ERαΔ3:ERα ratio might confer metastatic potential to the tumourigenic cells and promote neoangiogenesis. Future in vitro studies might be necessary to delineate such a mechanism, which could potentially be the basis of early intervention.

Fig. 1. Representative photomicrographs of immunohistochemical staining for γ-synuclein in human ovarian tissue by immunofluorescence over the range 500 nm - 540 nm for fluorescein (green) and 624 nm - 707 nm for PI (red)

(A) A high-grade serous adenocarcinoma (OV8). (B) A borderline mucinous ovarian cancer (OV3). (C) Epithelial cells at high magnification from a borderline mucinous ovarian cancer (OV3). (D) A borderline mucinous ovarian cancer (OV3) showing adjacent blood vessels. (E) Blood vessel at high magnification showing the majority of immunofluorescence was in the apical endothelial cells surrounding the blood vessel lumen. (F) Immunofluorescent image of blood vessel at high magnification superimposed on corresponding image derived using differential interference contrast microscopy. Scale bar: 20 μm.