Toll-Like Receptor 9 Agonists Promote Cellular Invasion by Increasing Matrix Metalloproteinase Activity

• Published in: Molecular cancer research Vol. 4; no. 7; pp. 437 - 447
• Main Authors: Merrell, Melinda A, Ilvesaro, Joanna M, Lehtonen, Niko, Sorsa, Timo, Gehrs, Bradley, Rosenthal, Eben, Chen, Dongquan, Shackley, Brit, Harris, Kevin W, Selander, Katri S
• Format: Journal Article
• Language: English
• Published: United States American Association for Cancer Research 01.07.2006
• Subjects: Antibodies - pharmacology; Astrocytoma - enzymology; Astrocytoma - pathology; Breast Neoplasms - enzymology; Breast Neoplasms - pathology; cancer; Cell Line, Tumor; Collagenases - immunology; Collagenases - metabolism; CpG Islands; DNA-Binding Proteins - genetics; Glioblastoma - enzymology; Glioblastoma - pathology; Humans; invasion; Matrix Metalloproteinase 13; Matrix Metalloproteinase 8 - metabolism; Matrix Metalloproteinase Inhibitors; Matrix Metalloproteinases - metabolism; Neoplasm Invasiveness; Oligonucleotides - genetics; Oligonucleotides - pharmacology; Toll-like receptor 9; Toll-Like Receptor 9 - agonists; Toll-Like Receptor 9 - biosynthesis; Toll-Like Receptor 9 - genetics; Toll-Like Receptor 9 - metabolism
• ISSN: 1541-7786; 1557-3125
• DOI: 10.1158/1541-7786.MCR-06-0007

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 μmol/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 ∼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. (Mol Cancer Res 2006;4(7):437–47)