Introduction
IL-1 receptor antagonist (IL-1RA) is IL-1 natural inhibitor and is encoded by the IL1RN gene. It has four variants; one secreted (sIL-1RA) and three intracellular forms (icIL-1RA1-3). Expression of IL1RA has been reported to be downregulated in many cancers including head and neck squamous cell carcinoma (HNSCC), but the effects of its downregulation in oral squamous cell carcinoma (OSCC) are largely unknown.
Methods: Using qPCR, western blot and immunofluorescence, we analysed the expression of total IL1RA, sIL-1RA, icIL-1RA, IL-1 receptor 1 (IL-1R1) and 2 (IL-1R2) expression in a panel of normal, dysplastic and cancerous oral keratinocytes cell lines under normal conditions and in response to IL-1α and IL-1β stimulation. We also assessed IL-1RA expression using formalin-fixed paraffin-embedded tissues samples from various stages of OSCC development. Transient transfection using a plasmid encoding icIL-1RA1 was performed on OSCC and oral dysplasia (OD) cell lines. Cell migration (by cell exclusion assay), cell proliferation (by EDU incorporation) and IL-6 and IL-8 production (by ELISA) were assessed.
Results: IL1RN is downregulated both at mRNA and protein levels (confirmed in vitro and in vivo) in OD and OSCC. icIL-1RA1 is the main isoform constitutively expressed in normal oral keratinocytes (NOK) cell lines. IL-1R1 mRNA expression is upregulated in cancer and dysplastic cell lines, but this was not seen at the protein level. Transient transfection of icIL-1RA1 in OSCC and OD cell lines has no or limited effects on cell migration, cell proliferation and production of IL-6 and IL-8.
Conclusion: IL1RN is downregulated in oral dysplasia and oral cancer. How this downregulation favours oral carcinogenesis and its phenotypic effects on cancer cells are not yet known.