IL-17 expression by breast-cancer-associated macrophages: IL-17 promotes invasiveness of breast cancer cell lines.
BACKGROUND
IL-17 plays an important role in autoimmunity, promoting autoimmunity, inflammation and invasion in multiple sclerosis, rheumatoid arthritis and type I diabetes. The role of IL-17 in cancer is unclear, however, as there are few studies examining IL-17 protein expression in cancer. We therefore examined IL-17 protein expression in human breast cancer and modelled its potential biological significance in vitro.


METHODS
Immunohistochemistry was used to determine IL-17 expression in breast cancers. Matrigel invasion assays were employed to examine the effect of IL-17 on cancer cell invasion by a panel of breast cancer cell lines. The role of matrix metalloproteinases (MMPs) was investigated with selective antagonists and immunoassays for MMP-2, MMP-3, MMP-9 and tissue inhibitor of MMP.


RESULTS
IL-17-expressing cells with macrophage morphology were identified in the peritumoural area of a proportion of patients (8/19 patients). Macrophages were confirmed by CD68 staining on serial sections. With the exception of occasional lymphocytes, one patient with rare multinucleate giant cells and one patient with occasional expression of IL-17 in tumour cells, no other IL-17-positive cells were detected. Addition of IL-17 to cell lines in vitro stimulated marked invasion of Matrigel. In contrast, IL-17 did not promote the invasion of MCF7 or T47D cell lines. Invasion was initially thought to be dependent on MMPs, as evidenced by the broad-spectrum MMP inhibitor GM6001 and selective antagonists of MMP-2/MMP-9 and MMP-3. Measurement of MMP-2, MMP-3 and MMP-9, and tissue inhibitor of MMP 1 secretion, failed to reveal any changes in expression following IL-17 exposure. In contrast, TNF promoted secretion of MMPs but IL-17 did not augment TNF, indicating that IL-17 acts via an independent mechanism.


CONCLUSIONS
The present study is the first to describe in situ expression of IL-17 protein in human breast tumours and to propose a direct association between IL-17 and breast cancer invasion. The precise effectors of IL-17-dependent invasion remain to be characterised but could include a range of proteases such as a disintegrin and metalloproteinase protein or astacins. Nevertheless, this work identifies a novel potential mechanism for breast cancer invasion and tumour progression, the prognostic implication of which is currently under investigation.
Zhu
XingWu
X
Academic Unit of Clinical Oncology, University of Nottingham - City Hospital Campus, Nottingham NG5 1PB, UK.
Mulcahy
Lori A
LA
Mohammed
Rabab A A
RA
Lee
Andrew H S
AH
Franks
Hester A
HA
Kilpatrick
Laura
L
Yilmazer
Acelya
A
Paish
E Claire
EC
Ellis
Ian O
IO
Patel
Poulam M
PM
Jackson
Andrew M
AM
D001943:Breast Neoplasms / Q000378:metabolism* / Q000473:pathology; D045744:Cell Line, Tumor; D003094:Collagen / Q000378:metabolism; D004338:Drug Combinations; D005260:Female; D006801:Humans; D007124:Immunoenzyme Techniques; D020381:Interleukin-17 / Q000378:metabolism*; D007797:Laminin / Q000378:metabolism; D008264:Macrophages / Q000378:metabolism*; D020782:Matrix Metalloproteinases / Q000378:metabolism; D009361:Neoplasm Invasiveness; D011509:Proteoglycans / Q000378:metabolism; D019715:Tissue Inhibitor of Metalloproteinase-1 / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D004338:Drug Combinations; D020381:Interleukin-17; D007797:Laminin; D011509:Proteoglycans; D019715:Tissue Inhibitor of Metalloproteinase-1; D014409:Tumor Necrosis Factor-alpha; C059485:matrigel; D003094:Collagen; D020782:Matrix Metalloproteinases