title: Toll-like receptor 9 agonists promote cellular invasion by increasing matrix metalloproteinase activity.
abstract: Toll-like receptor 9 (TLR9) recognizes microbial DNA. We show here that TLR9 protein is expressed in human breast cancer cells and clinical breast cancer samples. Stimulation of TLR9-expressing breast cancer cells with the TLR9 agonistic CpG oligonucleotides (1-10 mumol/L) dramatically increased their in vitro invasion in both Matrigel assays and three-dimensional collagen cultures. Similar effects on invasion were seen in TLR9-expressing astrocytoma and glioblastoma cells and in the immortalized human breast epithelial cell line MCF-10A. This effect was not, however, dependent on the CpG content of the TLR9 ligands because the non-CpG oligonucleotides induced invasion of TLR9-expressing cells. CpG or non-CpG oligonucleotide-induced invasion in MDA-MB-231 cells was blunted by chloroquine and they did not induce invasion of TLR9(-) breast cancer cells. Treatment of MDA-MB-231 cells with CpG or non-CpG oligonucleotides induced the formation of approximately 50-kDa gelatinolytic band in zymograms. This band and the increased invasion were abolished by a matrix metalloproteinase (MMP) inhibitor GM6001 but not by a serine proteinase inhibitor aprotinin. Furthermore, CpG oligonucleotide treatment decreased tissue inhibitor of metalloproteinase-3 expression and increased levels of active MMP-13 in TLR9-expressing but not TLR9(-) breast cancer cells without affecting MMP-8. Neutralizing anti-MMP-13 antibodies inhibited the CpG oligonucleotide-induced invasion. These findings suggest that infections may promote cancer progression through a novel TLR9-mediated mechanism. They also propose a new molecular target for cancer therapy, because TLR9 has not been associated with cancer invasiveness previously.
authors.affiliation: Division of Hematology-Oncology, Department of Medicine, University of Alabama at Birmingham, 35294-3300, USA.
authors.forename: Melinda A
authors.initials: MA
authors.lastname: Merrell
authors.forename: Joanna M
authors.initials: JM
authors.lastname: Ilvesaro
authors.forename: Niko
authors.initials: N
authors.lastname: Lehtonen
authors.forename: Timo
authors.initials: T
authors.lastname: Sorsa
authors.forename: Bradley
authors.initials: B
authors.lastname: Gehrs
authors.forename: Eben
authors.initials: E
authors.lastname: Rosenthal
authors.forename: Dongquan
authors.initials: D
authors.lastname: Chen
authors.forename: Brit
authors.initials: B
authors.lastname: Shackley
authors.forename: Kevin W
authors.initials: KW
authors.lastname: Harris
authors.forename: Katri S
authors.initials: KS
authors.lastname: Selander
mesh_terms: D000906:Antibodies / Q000494:pharmacology; D001254:Astrocytoma / Q000201:enzymology / Q000473:pathology; D001943:Breast Neoplasms / Q000201:enzymology* / Q000473:pathology; D045744:Cell Line, Tumor; D017364:Collagenases / Q000276:immunology / Q000378:metabolism; D018899:CpG Islands; D004268:DNA-Binding Proteins / Q000235:genetics; D005909:Glioblastoma / Q000201:enzymology / Q000473:pathology; D006801:Humans; D053509:Matrix Metalloproteinase 13; D020784:Matrix Metalloproteinase 8 / Q000378:metabolism; D061965:Matrix Metalloproteinase Inhibitors; D020782:Matrix Metalloproteinases / Q000378:metabolism*; D009361:Neoplasm Invasiveness; D009841:Oligonucleotides / Q000235:genetics / Q000494:pharmacology; D051217:Toll-Like Receptor 9 / Q000819:agonists* / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D015534:Trans-Activators
chemical_list: D000906:Antibodies; C409062:CXXC1 protein, human; D004268:DNA-Binding Proteins; D061965:Matrix Metalloproteinase Inhibitors; D009841:Oligonucleotides; C495371:TLR9 protein, human; D051217:Toll-Like Receptor 9; D015534:Trans-Activators; D017364:Collagenases; C507079:MMP13 protein, human; D053509:Matrix Metalloproteinase 13; D020782:Matrix Metalloproteinases; D020784:Matrix Metalloproteinase 8