Abstract
The increased expression of the Disintegrin and Metalloprotease ADAM12 has been associated with human cancers, however its role remain unclear. We have previously reported that ADAM12 expression is induced by the transforming growth factor, TGF-β and promotes TGF-β-dependent signaling through interaction with the type II receptor of TGF-β. Here we explore the implication of ADAM12 in TGF-β-mediated epithelial to mesenchymal transition (EMT), a key process in cancer progression. We show that ADAM12 expression is correlated with EMT markers in human breast cancer cell lines and biopsies. Using a non-malignant breast epithelial cell line (MCF10A), we demonstrate that TGF-β-induced EMT increases expression of the membrane-anchored ADAM12L long form. Importantly, ADAM12L overexpression in MCF10A is sufficient to induce loss of cell-cell contact, reorganization of actin cytoskeleton, up-regulation of EMT markers and chemoresistance. These effects are independent of the proteolytic activity but require the cytoplasmic tail and are specific of ADAM12L since overexpression of ADAM12S failed to induce similar changes. We further demonstrate that ADAM12L-dependent EMT is associated with increased phosphorylation of Smad3, Akt and ERK proteins. Conversely, inhibition of TGF-β receptors or ERK activities reverses ADAM12L-induced mesenchymal phenotype. Together our data demonstrate that ADAM12L is associated with EMT and contributes to TGF-β-dependent EMT by favoring both Smad-dependent and Smad-independent pathways.
Highlights
ADAM12 is a member of the ADAM protein family, a class of cell surface glycoproteins whose functions have been implicated with cell adhesion, PLOS ONE | DOI:10.1371/journal.pone.0139179 September 25, 2015ADAM12 and TGF-β-Induced epithelial to mesenchymal transition (EMT) migration, proteolysis and signaling [1]
We show that ADAM12 expression is correlated with expression of EMT markers in human breast tumor samples and breast cancer cell lines
As detailed in S2 Table, we identified 665 genes overexpressed in Basal B cells including ADAM12 and EMT-associated genes such as CDH2, SNAI2 and VIM
Summary
ADAM12 is a member of the ADAM (a metalloprotease and disintegrin) protein family, a class of cell surface glycoproteins whose functions have been implicated with cell adhesion, PLOS ONE | DOI:10.1371/journal.pone.0139179 September 25, 2015ADAM12 and TGF-β-Induced EMT migration, proteolysis and signaling [1]. Up-regulation of ADAM12 has been described in numerous cancers, including breast [2,3,4,5], colon [2], hepatocellular carcinomas [6], glioblastomas [7], stomach [2,8], oral cavity [9], bladder [10], lung [11,12] and giant cell tumors of bone [13]. ADAM12 has been shown to regulate tumor progression in mouse models either by increasing tumor cell resistance to apoptosis [3], by providing stromal support [14] or by inducing cell proliferation [15]. ADAM12 is considered as a negative prognosis marker for human bladder [10,17] and breast cancers [18,19] and is suggested to be an important player in tumor-stromal crosstalk that supports tumor progression [20]
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