title: GPER-1 acts as a tumor suppressor in ovarian cancer.
abstract: BACKGROUND
  It is known that the new membrane-bound estrogen receptor GPER-1 acts suppressive in breast cancer cells and its expression decreases during disease progression. This study was conducted to evaluate the GPER-1 expression in ovarian cancer and its correlation with progression. Its function was tested in vitro in ovarian cancer cells.
  
  
  METHODS
  GPER-1 expression was analyzed by immunohistochemistry in 35 benign ovarian tumors, 35 tumors of low-malignant potential and in 124 ovarian cancers. GPER-1 expression was correlated to the prospectively evaluated disease-free survival of ovarian cancer patients. We also tested GPER-1 expression in ovarian cancer cells and the effect of GPER-1 stimulation on cell growth.
  
  
  RESULTS
  GPER-1 expression was significantly lower in ovarian cancer tissue than in benign and low-malignant ovarian tumors. GPER-1 expression was observed in 83.1% of malignant tumors and was higher in early stage cancers and tumors with high histological differentiation. GPER-1 expression was associated with favourable clinical outcome. The difference in 2-year disease-free survival by GPER-1 expression was significant, 28.6% for GPER-1 negative and 59.2% for GPER-1 positive cases (p = 0.002). GPER-1 expression was observed in SKOV-3 and OVCAR-3 ovarian cancer cell lines. G-1, a selective GPER-1 agonist, suppressed proliferation of the two cell types via inhibition of cell cycle progression in G2/M phase and stimulation of caspase-dependent apoptosis. The blockade in G2/M phase was associated with increased expression of cyclin B1 and Cdc2 and phosphorylation of histone 3.
  
  
  CONCLUSIONS
  GPER-1 emerges as a new tumor suppressor with unsuspected therapeutic potential for ovarian cancer.
authors.affiliation: Department of Obstetrics and Gynecology, Otto-von-Guericke University, G,-Hauptmann Str, 35, 39108, Magdeburg, Germany. atanas.ignatov@gmail.com.
authors.forename: Tanja
authors.initials: T
authors.lastname: Ignatov
authors.forename: Saskia
authors.initials: S
authors.lastname: Modl
authors.forename: Maike
authors.initials: M
authors.lastname: Thulig
authors.forename: Christine
authors.initials: C
authors.lastname: Weißenborn
authors.forename: Oliver
authors.initials: O
authors.lastname: Treeck
authors.forename: Olaf
authors.initials: O
authors.lastname: Ortmann
authors.forename: Ac
authors.initials: A
authors.lastname: Zenclussen
authors.forename: Serban Dan
authors.initials: SD
authors.lastname: Costa
authors.forename: Thomas
authors.initials: T
authors.lastname: Kalinski
authors.forename: Atanas
authors.initials: A
authors.lastname: Ignatov