Iron regulates MMP-9 expression in oral squamous carcinoma cell lines

Abstract

Head and neck squamous cell carcinoma (HNSCC) is a highly invasive cancer with distant metastasis and a cause of great morbidity and mortality worldwide. Over-expression of matrix metalloproteinase (MMP)-9 is implicated in the invasion and metastasis of HNSCC. There are increasing evidence of an association between iron overload and cancer progression. However, the effect of iron on MMP-9 expression in HNSCC has not been studied. In the present study, we examined the effect of iron on MMP-9 expression in HNSCC cell lines, OM-2 and HN-22. Ferric ammonium citrate (FAC), a source of iron, at 15 µg/ml increased MMP-9 expression in both cell lines in a dose dependent manner as shown by reverse transcription polymerase chain reaction and gelatin zymography analyses. Studies using specific inhibitors of extracellular signal-regulated kinase (ERK) 1/2 and Akt demonstrated that iron regulated MMP-9 through ERK1/2 and Akt, and ERK1/2 was an upstream activator of Akt. Analysis of electrophoretic mobility shift assay revealed that iron induced MMP-9 expression by activation of activated protein-1 (AP-1). Since, application of neutralizing antibody against transferrin receptor-1 could not abolish the stimulated MMP-9 expression, this result suggested that iron uptake was non-transferrin dependent. In conclusion, this study was the first to demonstrate that MMP-9 was up-regulated by iron in HNSCC cell lines. We suggest that iron may be one of several factors that cause an increase of MMP-9 which is necessary for the development and progression of HNSCC.