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Updated: Jul 24, 2026

Spheroid Assay to Measure TGF-β-induced Invasion
Published on: November 16, 2011
Tamoxifen and estrogen effects on TGF-beta formation: role of thrombospondin-1, alphavbeta3, and integrin-associated
J G Harpel1, S Schultz-Cherry, J E Murphy-Ullrich
1Department of Cell Biology, New York University School of Medicine, 550 First Avenue, New York, New York 10016, USA.
Abstract:
We have found that the enhanced activation of latent TGF-beta by human breast carcinoma cell lines either treated with tamoxifen or deprived of estrogen is dependent upon thrombospondin-1 (TSP-1) since activation was blocked by anti-TSP-1 antibodies or by a TSP antagonist peptide. However, TGF-beta formation upon tamoxifen exposure to estrogen withdrawal is associated with decreased levels of soluble TSP-1. A concomitant increase in the expression of the TSP-1 receptors alphavbeta3 and integrin-associated protein (IAP) occurs under these conditions, and antibodies to TSP-1 or to these receptors inhibit increased TGF-beta formation. Therefore, increased cell surface associated TSP-1 enhances latent TGF-beta activation.
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