ADAM12 has recently emerged as a Candidate Cancer Gene in a comprehensive genetic analysis of human breast cancers. Three somatic mutations in ADAM12 were observed at significant frequencies in breast cancers: D301H, G479E and L792F. The first 2 of these mutations involve highly conserved residues in ADAM12, and our computational sequence analysis confirms that they may be cancer-related. We show that the corresponding mutations in mouse ADAM12 inhibit the proteolytic processing and activation of ADAM12 in NIH3T3, COS-7, CHO-K1 cells and in MCF-7 breast cancer cells. The D/H and G/E ADAM12 mutants exert a dominant-negative effect on the processing of the wild-type ADAM12. Immunofluorescence analysis and cell surface biotinylation experiments demonstrate that the D/H and G/E mutants are retained inside the cell and are not transported to the cell surface. Consequently, the D/H and G/E mutants, unlike the wild-type ADAM12, are not capable of shedding Delta-like l, a ligand for Notch receptor, at the cell surface, or of stimulating cell migration. Our results suggest that the breast cancer-associated mutations interfere with the intracellular trafficking of ADAM12 and result in loss of the functional ADAM12 at the cell surface. ' 2008 Wiley-Liss, Inc.Key words: proteolytic processing; cell surface; endoplasmic reticulum; intracellular trafficking Metalloprotease Disintegrin 12 (ADAM12) is highly expressed in cancer of the breast, 1,2 prostate, 3 liver, 4 stomach, 5 colon, 3 bladder 6 and in glioblastoma. 7 ADAM12 appears to be selectively upregulated in cancer cells, and its expression is nearly undetectable in normal breast, prostate, colon and liver epithelium. [1][2][3][4][5][6] In mouse models of breast, prostate and colon cancer, ADAM12 is found in a subpopulation of stromal cells adjacent to epithelial tumor cells. 2,3 Although this localization suggests that ADAM12 may play a role in stromal-tumor crosstalk, the molecular mechanism of ADAM12 action during cancer progression is not known.Studies utilizing mouse models of breast and prostate cancers suggested that ADAM12 promotes tumor progression. Forced expression of ADAM12 in breast tumors of MMTV-PyMT mice (carrying the polyomavirus middle T oncogene under mouse mammary tumor virus promoter and developing multifocal mammary adenocarcinomas) accelerated tumor progression. 2 Knocking out ADAM12 expression in prostate tumors of W10 mice (expressing SV40 large T-antigen under control of probasin promoter and developing prostate carcinomas) resulted in smaller and better differentiated tumors. 3 Recently, ADAM12 has been identified as one of the Candidate Cancer Genes in a comprehensive mutational analysis of human breast cancers. 8 Three mutations were found to be associated with breast cancer: D301H in the metalloprotease domain, G479E in the disintegrin domain and L792F in the cytoplasmic tail (Fig. 1a). The metalloprotease domain of ADAM12 is catalytically active and cleaves several protein substrates, including insulin growth factor-binding protein (IGFBP...
Increased expression of metalloprotease-disintegrin ADAM12 is a hallmark of several pathological conditions, including cancer, cardiovascular disease, and certain inflammatory diseases of the central nervous system or the muscoskeletal system. We show that transforming growth factor 1 (TGF1) is a potent inducer of ADAM12 mRNA and protein in mouse fibroblasts and in mouse and human mammary epithelial cells. Induction of ADAM12 is detected within 2 h of treatment with TGF1, is Smad2/Smad3-dependent, and is a result of derepression of the ADAM12, a member of the metalloprotease-disintegrin family of proteins, has been implicated in the progression of cancer, cardiovascular disease, osteoarthritis, and neurological disorders (1). The ADAM12 gene is frequently mutated in human breast cancers (2, 3), and cancer-associated mutations cause mislocalization of the ADAM12 protein in cells and alter its function (4). Missense single nuclear polymorphism in the ADAM12 gene shows strong association with osteoarthritis (5, 6). In addition to changes in its amino acid sequence, expression levels of ADAM12 are significantly increased in many pathological states. For example, ADAM12 expression levels are 20 -30-fold higher in human breast tumors than in normal mammary epithelium (7-12). ADAM12 expression is also markedly up-regulated in cancers of the liver, lung, stomach, colon, prostate, bladder, and in glioblastoma (13-18). Increased ADAM12 expression levels are found in the cardiac tissue of patients with hypertrophic obstructive cardiomyopathy (19) and in mice with angiotensin II-induced hypertension and cardiac hypertrophy (20,21). During inflammatory responses and aseptic osteolysis associated with loosened hip replacement implants, ADAM12 is up-regulated in the interface tissue around loosening implants (22). In experimental autoimmune encephalomyelitis, an animal model of multiple sclerosis, ADAM12 level is markedly increased in the T cells that infiltrate spinal cords (23).The mechanisms regulating ADAM12 expression, in particular those that may be responsible for altered levels of ADAM12 in various pathological states, are poorly understood. Previous studies employing hepatic stellate cells, a mesenchymal cell type in hepatic parenchyma, have indicated that ADAM12 expression is induced by transforming growth factor  (TGF) 2 (13, 24). The TGF signaling pathway is initiated when one of the family members, e.g. TGF1, -2, or -3, binds to a complex of TGF type I and type II serine/threonine kinase receptors (TRI and TRII, respectively) and induces phosphorylation and activation of TRI by TRII. TRI then phosphorylates receptor Smads (R-Smads), Smad2 and Smad3. Phosphorylated Smad2/3 associate with the common partner Smad4 and translocate to the nucleus, where they regulate transcription of target genes (25,26). In addition, receptor activation in certain cell types leads to Smad-independent responses via the activation of mitogen-activated protein kinases (MAPKs), phosphoinositide 3-kinase, and Rho family memb...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.