Degradation of ER-alpha by TGF-beta 1 could control tumor growth.(estrgen receptor, transforming growth factor)

2003 MAR 6 - (NewsRx.com & NewsRx.net) -- "Normal mammary epithelial cells are rapidly induced to G; they arrest by the widely expressed cytokine transforming growth factor beta (TGF-beta1). Studies in established breast cancer cell lines that express the estrogen receptor alpha (ERalpha) have demonstrated loss of this responsiveness. This inverse correlation suggests interpathway signaling important to cell growth and regulation," researchers in the United States report.

"The adenocarcinoma breast cell line BT474, which was not growth arrested by TGF-betal, was used as a model of estrogen inducible growth to explore interpathway crosstalk. Although BT474 cells were not growth arrested by TGF-beta1 as determined by flow cytometry analysis and 5'-bromo-3'-deoxyuridine incorporation into DNA, estrogen receptor protein levels were attenuated by 100 microM TGF-beta1 after 6 h. This decrease in ERalpha reached 50% of untreated control levels by 24 h of treatment and was further supported by a 50% decrease in estrogen inducible DNA synthesis. Inspection of ERalpha transcripts suggested that this decrease was primarily the result of altered ERalpha protein stability or availability. Use of the proteasome inhibitor, MG132, abolished all effects on ERalpha by TGF-beta1," wrote T.A. ...