The chemokine receptors CXCR1 and CXCR2 regulate oral cancer cell behaviour

Chemokines regulate physiological and pathological leucocyte trafficking, and chemokine receptors play a role in tumorigenesis. Expression of interleukin-8 (IL-8) receptors CXCR1 and CXCR2 has been shown in oral squamous cell carcinoma (OSCC) but remains poorly characterised. This aim of this study was to investigate CXCR1 and CXCR2 expression on normal oral keratinocytes (NOKs) and oral cancer cell lines (OCCL) and their relative response when exposed to IL-8 and growth-related oncogene-α (which selectively binds CXCR2).

mRNA and protein expression was studied using RT-PCR, immunocytochemistry and flow cytometry. ELISAs were used to investigate ERK1/2 phosphorylation and MMP production, whereas a MTS-based assay was employed to study proliferation. Migration assays were carried out using modified Boyden chambers with a matrigel coating used for invasion assays.

mRNA expression of CXCR1 and CXCR2 was seen in both NOKs and OCCL with significantly higher protein expression in OCCL. Exposure to IL-8 and GROα increased intracellular ERK phosphorylation, proliferation, migration and invasion with OCCL showing a greater response than NOKs. These effects were mediated through CXCR1 and CXCR2 (for IL-8) and CXCR2 (for GROα) as receptor-blocking antibodies significantly inhibited the responses. IL-8 and GROα also increased MMP-9 release from NOKs and OCCL with significantly higher amounts released by OCCL. However, an increase in MMP-7 production was only seen in OCCL.

Functional CXCR1 and CXCR2 exist on normal and cancerous oral epithelial cells, and our data suggests a role for these receptors in oral cancer biology.