Fibulin-3 is a novel TGF-? pathway inhibitor in the breast cancer microenvironment.
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ABSTRACT: Transforming growth factor-? (TGF-?) is an important regulator of breast cancer progression. However, how the breast cancer microenvironment regulates TGF-? signaling during breast cancer progression remains largely unknown. Here, we identified fibulin-3 as a secreted protein in the breast cancer microenvironment, which efficiently inhibits TGF-? signaling in both breast cancer cells and endothelial cells. Mechanistically, fibulin-3 interacts with the type I TGF-? receptor (T?RI) to block TGF-? induced complex formation of T?RI with the type II TGF-? receptor (T?RII) and subsequent downstream TGF-? signaling. Fibulin-3 expression decreases during breast cancer progression, with low fibulin-3 levels correlating with a poorer prognosis. Functionally, high fibulin-3 levels inhibited TGF-?-induced epithelial-mesenchymal transition (EMT), migration, invasion and endothelial permeability, while loss of fibulin-3 expression/function promoted these TGF-?-mediated effects. Further, restoring fibulin-3 expression in breast cancer cells inhibited TGF-? signaling, breast cancer cell EMT, invasion and metastasis in vivo. These studies provide a novel mechanism for how TGF-? signaling is regulated by the tumor microenvironment, and provide insight into targeting the TGF-? signaling pathway in human breast cancer patients.
SUBMITTER: Tian H
PROVIDER: S-EPMC4589427 | biostudies-literature | 2015 Nov
REPOSITORIES: biostudies-literature
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