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Multiple cells express interleukin 17 in oral squamous cell carcinoma

BACKGROUND
Interleukin (IL)-17 is a pro-inflammatory cytokine with pro- and antitumour effects. The aim of this study was to investigate the presence and potential sources of IL-17 in oral squamous cell carcinoma (OSCC).


METHODS
Immunohistochemistry was used to label and compare IL-17+ cells in the tissue sections of OSCC and inflammatory controls (IC), n = 14 for both. In OSCC, the comparison was made between the number of IL-17+ cells in the tumoral islands (TI), tumour-stroma interface (TS) and more distant stroma (DS). Cells expressing IL-17 were identified using double-labelling immunofluorescence and examined using laser scanning microscopy. The production of IL-17 from tumour cells was determined in the culture supernatants of OSCC cell lines, SCC4, SCC15 and SCC25, using sandwich ELISA.


RESULTS
Significantly more IL-17+ cells were observed in OSCC compared with IC (Mann-Whitney, P < 0.0001). In OSCC, the numbers of IL-17+ cells were not significantly different in three compartments, TI, TS and DS (one-way ANOVA, P > 0.05). However, the TI had significantly fewer IL-17+ cells than the combined stroma (both TS and DS together, Mann-Whitney, P < 0.01). Laser scanning microscopy revealed helper T cells, cytotoxic T cells, macrophages and mast cells co-expressed IL-17. ELISA experiments did not detect IL-17 in the supernatants of OSCC cell lines.


CONCLUSIONS
Although the tumour cells themselves did not express IL-17, a range of cell types did, suggesting multiple cellular sources for IL-17 in OSCC. The spatial distribution of IL-17+ cells suggests specific interactions with cells within the tumour microenvironment, implying that IL-17+ cells are likely to play a role in the pathogenesis of OSCC.