Betaglycan counters NFkB-mediated survival in human granulosa tumour cells (#148)
The molecular pathways which contribute to granulosa cell tumour (GCT) formation and survival are poorly understood. We have previously shown that the KGN cell line, derived from a metastatic GCT, exhibits constitutive nuclear factor kappa-B (NFκB) activity, which is pro-survival (1). We have also shown that KGN cells exhibit reduced expression of betaglycan, the transforming growth factor-beta (TGFß) accessory receptor, and that loss of this receptor is linked to insensitivity to TGFß and increased tumour aggressiveness (2). In the current work, we test the hypothesis that the NFκB- and TGFß/betaglycan-mediated pathways counterbalance each other to govern GCT survival. We firstly examined the effects of NFκB inhibition by BAY11-7082 (5 μM) on the viability of KGN cells stably transfected with either a vector control or betaglycan expression construct. Overnight treatment with BAY11-7082 resulted in the suppression of NFκB activity and a significant 2-fold increase in caspase 3/7 activation in the betaglycan-expressing cells relative to the control cell line. Accordingly, BAY11-7082-treated betaglycan-expressing cells exhibited a decrease in cells cycling (15%; p<0.05) and an increase in cell death (300%; p<0.05) relative to controls. Furthermore, in BAY11-7082-treated control cells, TGFß2 dose-dependently decreased cell viability, and this was significantly enhanced by the presence of betaglycan. Intriguingly, TGFß2 significantly enhanced basal NFκB activity in control cells in luciferase reporter assays. In contrast, expression of betaglycan in KGN cells suppressed both basal and TGFß2-stimulated NFκB activity. This analysis showed that betaglycan is a key determinant of the functional outcomes of NFκB and TGFß2 interactions in GCT cells, and its loss with tumour progression likely contributes to GCT tumorigenicity by enhancing NFκB activity. Supported by the NHMRC (338516; 494802; 441101; 1002559); OCRF, and Victorian Government's Operational Infrastructure Support Program.
1. Chu, S. et al., (2004). Mol Endocrinol. 18, 1919-1928
2. Bilandzic, M. et al., (2009) Mol Endocrinol. 23, 539-548