Transforming Growth Factor-β1-Mediated Activation of NF-κB Contributes to Enhanced ADAM-12 Expression in Mammary Carcinoma Cells

A disintegrin and metalloproteinase-12 (ADAM-12), a member of multifunctional family of proteins, is upregulated in many cancers, including breast, lung, liver, prostate, gastric, and bladder. The multidomain structure, composed of a prodomain, a metalloproteinase, disintegrin-like, epidermal growth factor-like, cysteine-rich and transmembrane domains, and a cytoplasmic tail, allows ADAM-12 to promote matrix degradation, cell-cell adhesion, and intracellular signaling capacities and thereby to play a critical role in cancer growth and metastasis. Despite ample evidence linking increased ADAM-12 expression with cancer, the mechanisms controlling its upregulation are still unknown. In the present study, transforming growth factor-beta 1 (TGF-beta 1) is shown to increase ADAM-12 mRNA expression in MDA-MB-231 breast carcinoma cells. We have identified a promoter element responsible for TGF-beta 1-mediated ADAM-12 induction. We show interaction of NF-kappa B with ADAM-12 promoter and that high level of NF-kappa B activity in breast carcinoma cells results in the upregulation of ADAM-12 expression. Site-directed mutagenesis of the NF-kappa B element in ADAM-12 promoter and inhibition of NF-kappa B activity by Bay-11-7085 and MG-132 significantly reduced TGF-beta 1-mediated increase of ADAM-12 promoter-driven gene expression. Transfection of cells with a dominant-negative mutant form of I kappa B alpha (I kappa B alpha Delta N), which inhibits activation of NF-kappa B, significantly reduced transcription from ADAM-12 promoter-reporter in TGF-beta 1-stimulated MDA-MB-231 cancer cells. In correlation, overexpression of NF-kappa B induced ADAM-12 expression in a dose-dependent manner. DNA-binding and ChIP assays indicated that p65 subunit of NF-kappa B binds to ADAM-12 promoter. Together, our study identified a cellular mechanism for induction of ADAM-12, which involves NF-kappa B and its activation by TGF-beta 1. Mol Cancer Res; 8(9); 1261-70. (C)2010 AACR.