Betaglycan Alters NFκB-TGFβ2 Cross Talk to Reduce Survival of Human Granulosa Tumor Cells

Mol Endocrinol. 2013 Mar;27(3):466-79. doi: 10.1210/me.2012-1239. Epub 2013 Jan 15.

Abstract

The molecular pathways controlling granulosa cell tumor (GCT) survival are poorly understood. In many cell types, nuclear factor-κB (NFκB) and TGFβ coordinately regulate cell survival to maintain tissue homeostasis. Because GCT cell lines exhibit constitutively activated NFκB, we hypothesized that NFκB blocks TGFβ-mediated cell death in GCT cells. To test this hypothesis, we used the human GCT cell line KGN, which exhibits loss of betaglycan, a TGFβ co-receptor. After inhibition of NFκB in KGN cells, re-expression of betaglycan resulted in a decrease in cell viability, which was further decreased by TGFβ2. Intriguingly, TGFβ2 increased NFκB reporter activity in control cells, but betaglycan expression suppressed both basal and TGFβ2-stimulated NFκB activity. Chemical inhibition of Mothers against decapentaplegic homolog 2/3 (SMAD2/3) signaling or SMAD2/3 gene silencing revealed that both SMADs contributed to cell survival. Furthermore, inhibiting NFκB activity resulted in a specific reduction in SMAD3 expression. Conversely, overexpression of SMAD3 increased basal NFκB activity and countered betaglycan-mediated suppression of NFκB activity. Finally, ERK1/2 activation emerged as the point of convergence of NFκB, SMAD3, and TGFβ2/betaglycan governance of GCT cell viability. Key findings in KGN cells were reproduced in a second GCT cell line, COV434. Collectively, our data establish that both SMAD2/3 and NFκB signaling pathways support GCT cell viability and suggest the existence of a positive feedback loop between NFκB and SMAD3 signaling in late-stage GCT. Furthermore, our data suggest that loss of betaglycan during tumor progression in GCT alters the functional outcomes generated by NFκB and TGFβ pathway cross talk.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Apoptosis
  • Cell Line, Tumor
  • Cell Survival
  • Extracellular Signal-Regulated MAP Kinases / metabolism
  • Female
  • Granulosa Cell Tumor / enzymology
  • Granulosa Cell Tumor / metabolism*
  • Granulosa Cell Tumor / pathology*
  • Humans
  • Models, Biological
  • NF-kappa B / antagonists & inhibitors
  • NF-kappa B / metabolism*
  • Proteoglycans / metabolism*
  • Receptors, Transforming Growth Factor beta / metabolism*
  • Signal Transduction
  • Smad Proteins / metabolism
  • Transforming Growth Factor beta2 / metabolism*

Substances

  • NF-kappa B
  • Proteoglycans
  • Receptors, Transforming Growth Factor beta
  • Smad Proteins
  • Transforming Growth Factor beta2
  • betaglycan
  • Extracellular Signal-Regulated MAP Kinases