A14
Loss of WWOX causes aberrant PKB/Akt signalling and enhanced survival in ovarian cancer cells
Carol Ward1, Adam Paige2, Szymon Jancazar2, Charlie Gourley1
1University of Edinbugh, Edinburgh, UK, 2Imperial College London, London, UK
Background
The WW domain-containing oxidoreductase (WWOX) gene acts as a tumour suppressor in ovarian cancer cells, decreasing tumourigenicity in vivo, 3 downregulation α and adhesion and migration, via integrin in vitro. WWOX increased apoptosis in these cells when cultured under non-adherent conditions, suggesting that WWOX interferes with survival signals engaged by cell/ECM interactions. This study determined the effect of WWOX on intracellular survival pathways activated by integrin-mediated adhesion.
Method
WWOX-dependent differences in cell/ECM signalling interactions were examined by comparing PEO1 ovarian cancer cells in which WWOX is homozygously deleted and WWOX-transfected PEO1 cells, using Western blots to determine a) alterations in protein expression and b) changes in the phosphorylation status of specific residues involved in activation of target proteins in adhesion/survival pathways.
Results
Adhesion studies determined that differences in PKB/Akt signalling occurred between WWOX-positive and negative cells. AktSer473 was phosphorylated in both clones, but AktThr308 phosphorylation was deficient in negative cells, although several Akt substrates were effectively activated regardless of WWOX status. PDK1 was active in both clones, suggesting that AktThr308 should be phosphorylated in WWOX-negative cells. WWOX-negative cells displayed active PTEN, when compared with WWOX positive cells, but showed increasing phosphorylation of AktSer473 illustrating that activation and deactivation of Akt is aberrant in the absence of WWOX. WWOX-negative cells exhibited increased levels of the Akt substrate PRAS40 and elevated phosphorylation of this pro-apoptotic protein in adhesion assays. WWOX siRNA treatment significantly increased PRAS40 expression in WWOX-positive cells.
Conclusion
WWOX expression changes Akt signalling in response to adhesion and negatively influences expression and phosphorylation of PRAS40, conferring a tumour suppressive effect in ovarian cancer by increasing apoptosis.
