title: Preferential effect of akt2-dependent signaling on the cellular viability of ovarian cancer cells in response to EGF.
abstract: OBJECTIVE
  Overexpression of the epidermal growth factor receptor (EGFR) is associated with the malignant phenotype in many cancers including ovarian cancer, which leads to increased cell proliferation and survival. In spite of emerging EGFR inhibitors as a potentially useful agent, they are largely ineffective in patients with advanced or recurrent ovarian cancers. Since Akt as a key downstream factor of EGFR is highly activated in some high grade serous ovarian tumors, the augmented Akt activation may attribute to irregular EGFR-mediated signaling observed in ovarian cancer. Here we investigated the differential effect of Akt on the EGF-induced cell viability in a panel of ovarian cancer cell lines.
  
  
  METHODS
  Cellular viability assay and western blot analysis were used to measure cell viability and expression levels of proteins, respectively. Knockdown of Akt was achieved with siRNA and stable transfection of expression vectors was performed.
  
  
  RESULTS
  Cellular viability increased in OVCAR-3 ovarian cancer cells exposed to EGF, but little to no difference was observed in the 5 other ovarian cancer cells including SKOV-3 cells despite of the expression of EGFR. In OVCAR-3 cells, EGF activated Erk and Akt, but an Erk inhibitor had no impact on cellular viability. On the other hand, the EGFR and PI3K inhibitors decreased EGF-induced cellular viability, indicating the involvement of Akt signaling. Although EGF activated Erk in SKOV-3 cells, the Akt activation was very weak as compared to OVCAR-3 cells. Furthermore, we observed a different expression of Akt isoforms: Akt1 was constitutively expressed in all tested ovarian cancer cells, while Akt3 was little expressed. Interestingly, Akt2 was highly expressed in OVCAR-3 cells. Knockdown of Akt2 blocked EGF-induced OVCAR-3 cell viability whereas knockdown for Akt1 and Erk1/2 had no significant effect. Stable transfection of Akt2 into SKOV-3 cells phosphorylated more Akt and enhanced cell viability in response to EGF.
  
  
  CONCLUSIONS
  Akt2-dependent signaling appears to play an important role in EGFR-mediated cellular viability in ovarian cancer and targeting specific Akt isoform may provide a potential therapeutic approach for EGFR-expressing ovarian cancers.
authors.affiliation: 1. Department of Obstetrics and Gynecology, Vanderbilt University Medical Center, Nashville, TN, USA;
authors.forename: Dineo
authors.initials: D
authors.lastname: Khabele
authors.affiliation: 2. Department of Biochemistry and Cancer Biology, Meharry Medical College, Nashville, TN, USA;
authors.forename: Syeda M
authors.initials: SM
authors.lastname: Kabir
authors.affiliation: 2. Department of Biochemistry and Cancer Biology, Meharry Medical College, Nashville, TN, USA;
authors.forename: Yuanlin
authors.initials: Y
authors.lastname: Dong
authors.affiliation: 3. Department of Physiology, Meharry Medical College, Nashville, TN, USA;
authors.forename: Eunsook
authors.initials: E
authors.lastname: Lee
authors.affiliation: 4. Department of Medicine, Morehouse College of Medicine, Atlanta, GA, USA.
authors.forename: Valerie Montgomery
authors.initials: VM
authors.lastname: Rice
authors.affiliation: 2. Department of Biochemistry and Cancer Biology, Meharry Medical College, Nashville, TN, USA;
authors.forename: Deok-Soo
authors.initials: DS
authors.lastname: Son
keywords: Akt; EGFR; Erk; cell viability; ovarian cancer.